TOMOYO Linux Cross Reference
Linux/kernel/fork.c

   // SPDX-License-Identifier: GPL-2.0-only
   /*
    *  linux/kernel/fork.c
    *
    *  Copyright (C) 1991, 1992  Linus Torvalds
    */
   
   /*
    *  'fork.c' contains the help-routines for the 'fork' system call
   * (see also entry.S and others).
   * Fork is rather simple, once you get the hang of it, but the memory
   * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
   */
  
  #include <linux/anon_inodes.h>
  #include <linux/slab.h>
  #include <linux/sched/autogroup.h>
  #include <linux/sched/mm.h>
  #include <linux/sched/coredump.h>
  #include <linux/sched/user.h>
  #include <linux/sched/numa_balancing.h>
  #include <linux/sched/stat.h>
  #include <linux/sched/task.h>
  #include <linux/sched/task_stack.h>
  #include <linux/sched/cputime.h>
  #include <linux/seq_file.h>
  #include <linux/rtmutex.h>
  #include <linux/init.h>
  #include <linux/unistd.h>
  #include <linux/module.h>
  #include <linux/vmalloc.h>
  #include <linux/completion.h>
  #include <linux/personality.h>
  #include <linux/mempolicy.h>
  #include <linux/sem.h>
  #include <linux/file.h>
  #include <linux/fdtable.h>
  #include <linux/iocontext.h>
  #include <linux/key.h>
  #include <linux/kmsan.h>
  #include <linux/binfmts.h>
  #include <linux/mman.h>
  #include <linux/mmu_notifier.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/mm_inline.h>
  #include <linux/memblock.h>
  #include <linux/nsproxy.h>
  #include <linux/capability.h>
  #include <linux/cpu.h>
  #include <linux/cgroup.h>
  #include <linux/security.h>
  #include <linux/hugetlb.h>
  #include <linux/seccomp.h>
  #include <linux/swap.h>
  #include <linux/syscalls.h>
  #include <linux/syscall_user_dispatch.h>
  #include <linux/jiffies.h>
  #include <linux/futex.h>
  #include <linux/compat.h>
  #include <linux/kthread.h>
  #include <linux/task_io_accounting_ops.h>
  #include <linux/rcupdate.h>
  #include <linux/ptrace.h>
  #include <linux/mount.h>
  #include <linux/audit.h>
  #include <linux/memcontrol.h>
  #include <linux/ftrace.h>
  #include <linux/proc_fs.h>
  #include <linux/profile.h>
  #include <linux/rmap.h>
  #include <linux/ksm.h>
  #include <linux/acct.h>
  #include <linux/userfaultfd_k.h>
  #include <linux/tsacct_kern.h>
  #include <linux/cn_proc.h>
  #include <linux/freezer.h>
  #include <linux/delayacct.h>
  #include <linux/taskstats_kern.h>
  #include <linux/tty.h>
  #include <linux/fs_struct.h>
  #include <linux/magic.h>
  #include <linux/perf_event.h>
  #include <linux/posix-timers.h>
  #include <linux/user-return-notifier.h>
  #include <linux/oom.h>
  #include <linux/khugepaged.h>
  #include <linux/signalfd.h>
  #include <linux/uprobes.h>
  #include <linux/aio.h>
  #include <linux/compiler.h>
  #include <linux/sysctl.h>
  #include <linux/kcov.h>
  #include <linux/livepatch.h>
  #include <linux/thread_info.h>
  #include <linux/stackleak.h>
  #include <linux/kasan.h>
  #include <linux/scs.h>
  #include <linux/io_uring.h>
 #include <linux/bpf.h>
 #include <linux/stackprotector.h>
 #include <linux/user_events.h>
 #include <linux/iommu.h>
 #include <linux/rseq.h>
 #include <uapi/linux/pidfd.h>
 #include <linux/pidfs.h>
 
 #include <asm/pgalloc.h>
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
 #include <trace/events/sched.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/task.h>
 
 #include <kunit/visibility.h>
 
 /*
  * Minimum number of threads to boot the kernel
  */
 #define MIN_THREADS 20
 
 /*
  * Maximum number of threads
  */
 #define MAX_THREADS FUTEX_TID_MASK
 
 /*
  * Protected counters by write_lock_irq(&tasklist_lock)
  */
 unsigned long total_forks;      /* Handle normal Linux uptimes. */
 int nr_threads;                 /* The idle threads do not count.. */
 
 static int max_threads;         /* tunable limit on nr_threads */
 
 #define NAMED_ARRAY_INDEX(x)    [x] = __stringify(x)
 
 static const char * const resident_page_types[] = {
         NAMED_ARRAY_INDEX(MM_FILEPAGES),
         NAMED_ARRAY_INDEX(MM_ANONPAGES),
         NAMED_ARRAY_INDEX(MM_SWAPENTS),
         NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
 };
 
 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 
 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 
 #ifdef CONFIG_PROVE_RCU
 int lockdep_tasklist_lock_is_held(void)
 {
         return lockdep_is_held(&tasklist_lock);
 }
 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 #endif /* #ifdef CONFIG_PROVE_RCU */
 
 int nr_processes(void)
 {
         int cpu;
         int total = 0;
 
         for_each_possible_cpu(cpu)
                 total += per_cpu(process_counts, cpu);
 
         return total;
 }
 
 void __weak arch_release_task_struct(struct task_struct *tsk)
 {
 }
 
 static struct kmem_cache *task_struct_cachep;
 
 static inline struct task_struct *alloc_task_struct_node(int node)
 {
         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 }
 
 static inline void free_task_struct(struct task_struct *tsk)
 {
         kmem_cache_free(task_struct_cachep, tsk);
 }
 
 /*
  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
  * kmemcache based allocator.
  */
 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
 
 #  ifdef CONFIG_VMAP_STACK
 /*
  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
  * flush.  Try to minimize the number of calls by caching stacks.
  */
 #define NR_CACHED_STACKS 2
 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 
 struct vm_stack {
         struct rcu_head rcu;
         struct vm_struct *stack_vm_area;
 };
 
 static bool try_release_thread_stack_to_cache(struct vm_struct *vm)
 {
         unsigned int i;
 
         for (i = 0; i < NR_CACHED_STACKS; i++) {
                 struct vm_struct *tmp = NULL;
 
                 if (this_cpu_try_cmpxchg(cached_stacks[i], &tmp, vm))
                         return true;
         }
         return false;
 }
 
 static void thread_stack_free_rcu(struct rcu_head *rh)
 {
         struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
 
         if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
                 return;
 
         vfree(vm_stack);
 }
 
 static void thread_stack_delayed_free(struct task_struct *tsk)
 {
         struct vm_stack *vm_stack = tsk->stack;
 
         vm_stack->stack_vm_area = tsk->stack_vm_area;
         call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
 }
 
 static int free_vm_stack_cache(unsigned int cpu)
 {
         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
         int i;
 
         for (i = 0; i < NR_CACHED_STACKS; i++) {
                 struct vm_struct *vm_stack = cached_vm_stacks[i];
 
                 if (!vm_stack)
                         continue;
 
                 vfree(vm_stack->addr);
                 cached_vm_stacks[i] = NULL;
         }
 
         return 0;
 }
 
 static int memcg_charge_kernel_stack(struct vm_struct *vm)
 {
         int i;
         int ret;
         int nr_charged = 0;
 
         BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 
         for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
                 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
                 if (ret)
                         goto err;
                 nr_charged++;
         }
         return 0;
 err:
         for (i = 0; i < nr_charged; i++)
                 memcg_kmem_uncharge_page(vm->pages[i], 0);
         return ret;
 }
 
 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 {
         struct vm_struct *vm;
         void *stack;
         int i;
 
         for (i = 0; i < NR_CACHED_STACKS; i++) {
                 struct vm_struct *s;
 
                 s = this_cpu_xchg(cached_stacks[i], NULL);
 
                 if (!s)
                         continue;
 
                 /* Reset stack metadata. */
                 kasan_unpoison_range(s->addr, THREAD_SIZE);
 
                 stack = kasan_reset_tag(s->addr);
 
                 /* Clear stale pointers from reused stack. */
                 memset(stack, 0, THREAD_SIZE);
 
                 if (memcg_charge_kernel_stack(s)) {
                         vfree(s->addr);
                         return -ENOMEM;
                 }
 
                 tsk->stack_vm_area = s;
                 tsk->stack = stack;
                 return 0;
         }
 
         /*
          * Allocated stacks are cached and later reused by new threads,
          * so memcg accounting is performed manually on assigning/releasing
          * stacks to tasks. Drop __GFP_ACCOUNT.
          */
         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
                                      VMALLOC_START, VMALLOC_END,
                                      THREADINFO_GFP & ~__GFP_ACCOUNT,
                                      PAGE_KERNEL,
                                      0, node, __builtin_return_address(0));
         if (!stack)
                 return -ENOMEM;
 
         vm = find_vm_area(stack);
         if (memcg_charge_kernel_stack(vm)) {
                 vfree(stack);
                 return -ENOMEM;
         }
         /*
          * We can't call find_vm_area() in interrupt context, and
          * free_thread_stack() can be called in interrupt context,
          * so cache the vm_struct.
          */
         tsk->stack_vm_area = vm;
         stack = kasan_reset_tag(stack);
         tsk->stack = stack;
         return 0;
 }
 
 static void free_thread_stack(struct task_struct *tsk)
 {
         if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
                 thread_stack_delayed_free(tsk);
 
         tsk->stack = NULL;
         tsk->stack_vm_area = NULL;
 }
 
 #  else /* !CONFIG_VMAP_STACK */
 
 static void thread_stack_free_rcu(struct rcu_head *rh)
 {
         __free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
 }
 
 static void thread_stack_delayed_free(struct task_struct *tsk)
 {
         struct rcu_head *rh = tsk->stack;
 
         call_rcu(rh, thread_stack_free_rcu);
 }
 
 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 {
         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
                                              THREAD_SIZE_ORDER);
 
         if (likely(page)) {
                 tsk->stack = kasan_reset_tag(page_address(page));
                 return 0;
         }
         return -ENOMEM;
 }
 
 static void free_thread_stack(struct task_struct *tsk)
 {
         thread_stack_delayed_free(tsk);
         tsk->stack = NULL;
 }
 
 #  endif /* CONFIG_VMAP_STACK */
 # else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
 
 static struct kmem_cache *thread_stack_cache;
 
 static void thread_stack_free_rcu(struct rcu_head *rh)
 {
         kmem_cache_free(thread_stack_cache, rh);
 }
 
 static void thread_stack_delayed_free(struct task_struct *tsk)
 {
         struct rcu_head *rh = tsk->stack;
 
         call_rcu(rh, thread_stack_free_rcu);
 }
 
 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 {
         unsigned long *stack;
         stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
         stack = kasan_reset_tag(stack);
         tsk->stack = stack;
         return stack ? 0 : -ENOMEM;
 }
 
 static void free_thread_stack(struct task_struct *tsk)
 {
         thread_stack_delayed_free(tsk);
         tsk->stack = NULL;
 }
 
 void thread_stack_cache_init(void)
 {
         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
                                         THREAD_SIZE, NULL);
         BUG_ON(thread_stack_cache == NULL);
 }
 
 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
 
 /* SLAB cache for signal_struct structures (tsk->signal) */
 static struct kmem_cache *signal_cachep;
 
 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 struct kmem_cache *sighand_cachep;
 
 /* SLAB cache for files_struct structures (tsk->files) */
 struct kmem_cache *files_cachep;
 
 /* SLAB cache for fs_struct structures (tsk->fs) */
 struct kmem_cache *fs_cachep;
 
 /* SLAB cache for vm_area_struct structures */
 static struct kmem_cache *vm_area_cachep;
 
 /* SLAB cache for mm_struct structures (tsk->mm) */
 static struct kmem_cache *mm_cachep;
 
 #ifdef CONFIG_PER_VMA_LOCK
 
 /* SLAB cache for vm_area_struct.lock */
 static struct kmem_cache *vma_lock_cachep;
 
 static bool vma_lock_alloc(struct vm_area_struct *vma)
 {
         vma->vm_lock = kmem_cache_alloc(vma_lock_cachep, GFP_KERNEL);
         if (!vma->vm_lock)
                 return false;
 
         init_rwsem(&vma->vm_lock->lock);
         vma->vm_lock_seq = -1;
 
         return true;
 }
 
 static inline void vma_lock_free(struct vm_area_struct *vma)
 {
         kmem_cache_free(vma_lock_cachep, vma->vm_lock);
 }
 
 #else /* CONFIG_PER_VMA_LOCK */
 
 static inline bool vma_lock_alloc(struct vm_area_struct *vma) { return true; }
 static inline void vma_lock_free(struct vm_area_struct *vma) {}
 
 #endif /* CONFIG_PER_VMA_LOCK */
 
 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
 {
         struct vm_area_struct *vma;
 
         vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
         if (!vma)
                 return NULL;
 
         vma_init(vma, mm);
         if (!vma_lock_alloc(vma)) {
                 kmem_cache_free(vm_area_cachep, vma);
                 return NULL;
         }
 
         return vma;
 }
 
 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 {
         struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 
         if (!new)
                 return NULL;
 
         ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
         ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
         /*
          * orig->shared.rb may be modified concurrently, but the clone
          * will be reinitialized.
          */
         data_race(memcpy(new, orig, sizeof(*new)));
         if (!vma_lock_alloc(new)) {
                 kmem_cache_free(vm_area_cachep, new);
                 return NULL;
         }
         INIT_LIST_HEAD(&new->anon_vma_chain);
         vma_numab_state_init(new);
         dup_anon_vma_name(orig, new);
 
         return new;
 }
 
 void __vm_area_free(struct vm_area_struct *vma)
 {
         vma_numab_state_free(vma);
         free_anon_vma_name(vma);
         vma_lock_free(vma);
         kmem_cache_free(vm_area_cachep, vma);
 }
 
 #ifdef CONFIG_PER_VMA_LOCK
 static void vm_area_free_rcu_cb(struct rcu_head *head)
 {
         struct vm_area_struct *vma = container_of(head, struct vm_area_struct,
                                                   vm_rcu);
 
         /* The vma should not be locked while being destroyed. */
         VM_BUG_ON_VMA(rwsem_is_locked(&vma->vm_lock->lock), vma);
         __vm_area_free(vma);
 }
 #endif
 
 void vm_area_free(struct vm_area_struct *vma)
 {
 #ifdef CONFIG_PER_VMA_LOCK
         call_rcu(&vma->vm_rcu, vm_area_free_rcu_cb);
 #else
         __vm_area_free(vma);
 #endif
 }
 
 static void account_kernel_stack(struct task_struct *tsk, int account)
 {
         if (IS_ENABLED(CONFIG_VMAP_STACK)) {
                 struct vm_struct *vm = task_stack_vm_area(tsk);
                 int i;
 
                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
                         mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
                                               account * (PAGE_SIZE / 1024));
         } else {
                 void *stack = task_stack_page(tsk);
 
                 /* All stack pages are in the same node. */
                 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
                                       account * (THREAD_SIZE / 1024));
         }
 }
 
 void exit_task_stack_account(struct task_struct *tsk)
 {
         account_kernel_stack(tsk, -1);
 
         if (IS_ENABLED(CONFIG_VMAP_STACK)) {
                 struct vm_struct *vm;
                 int i;
 
                 vm = task_stack_vm_area(tsk);
                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
                         memcg_kmem_uncharge_page(vm->pages[i], 0);
         }
 }
 
 static void release_task_stack(struct task_struct *tsk)
 {
         if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
                 return;  /* Better to leak the stack than to free prematurely */
 
         free_thread_stack(tsk);
 }
 
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 void put_task_stack(struct task_struct *tsk)
 {
         if (refcount_dec_and_test(&tsk->stack_refcount))
                 release_task_stack(tsk);
 }
 #endif
 
 void free_task(struct task_struct *tsk)
 {
 #ifdef CONFIG_SECCOMP
         WARN_ON_ONCE(tsk->seccomp.filter);
 #endif
         release_user_cpus_ptr(tsk);
         scs_release(tsk);
 
 #ifndef CONFIG_THREAD_INFO_IN_TASK
         /*
          * The task is finally done with both the stack and thread_info,
          * so free both.
          */
         release_task_stack(tsk);
 #else
         /*
          * If the task had a separate stack allocation, it should be gone
          * by now.
          */
         WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
 #endif
         rt_mutex_debug_task_free(tsk);
         ftrace_graph_exit_task(tsk);
         arch_release_task_struct(tsk);
         if (tsk->flags & PF_KTHREAD)
                 free_kthread_struct(tsk);
         bpf_task_storage_free(tsk);
         free_task_struct(tsk);
 }
 EXPORT_SYMBOL(free_task);
 
 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
 {
         struct file *exe_file;
 
         exe_file = get_mm_exe_file(oldmm);
         RCU_INIT_POINTER(mm->exe_file, exe_file);
 }
 
 #ifdef CONFIG_MMU
 static __latent_entropy int dup_mmap(struct mm_struct *mm,
                                         struct mm_struct *oldmm)
 {
         struct vm_area_struct *mpnt, *tmp;
         int retval;
         unsigned long charge = 0;
         LIST_HEAD(uf);
         VMA_ITERATOR(vmi, mm, 0);
 
         uprobe_start_dup_mmap();
         if (mmap_write_lock_killable(oldmm)) {
                 retval = -EINTR;
                 goto fail_uprobe_end;
         }
         flush_cache_dup_mm(oldmm);
         uprobe_dup_mmap(oldmm, mm);
         /*
          * Not linked in yet - no deadlock potential:
          */
         mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
 
         /* No ordering required: file already has been exposed. */
         dup_mm_exe_file(mm, oldmm);
 
         mm->total_vm = oldmm->total_vm;
         mm->data_vm = oldmm->data_vm;
         mm->exec_vm = oldmm->exec_vm;
         mm->stack_vm = oldmm->stack_vm;
 
         retval = ksm_fork(mm, oldmm);
         if (retval)
                 goto out;
         khugepaged_fork(mm, oldmm);
 
         /* Use __mt_dup() to efficiently build an identical maple tree. */
         retval = __mt_dup(&oldmm->mm_mt, &mm->mm_mt, GFP_KERNEL);
         if (unlikely(retval))
                 goto out;
 
         mt_clear_in_rcu(vmi.mas.tree);
         for_each_vma(vmi, mpnt) {
                 struct file *file;
 
                 vma_start_write(mpnt);
                 if (mpnt->vm_flags & VM_DONTCOPY) {
                         retval = vma_iter_clear_gfp(&vmi, mpnt->vm_start,
                                                     mpnt->vm_end, GFP_KERNEL);
                         if (retval)
                                 goto loop_out;
 
                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
                         continue;
                 }
                 charge = 0;
                 /*
                  * Don't duplicate many vmas if we've been oom-killed (for
                  * example)
                  */
                 if (fatal_signal_pending(current)) {
                         retval = -EINTR;
                         goto loop_out;
                 }
                 if (mpnt->vm_flags & VM_ACCOUNT) {
                         unsigned long len = vma_pages(mpnt);
 
                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
                                 goto fail_nomem;
                         charge = len;
                 }
                 tmp = vm_area_dup(mpnt);
                 if (!tmp)
                         goto fail_nomem;
                 retval = vma_dup_policy(mpnt, tmp);
                 if (retval)
                         goto fail_nomem_policy;
                 tmp->vm_mm = mm;
                 retval = dup_userfaultfd(tmp, &uf);
                 if (retval)
                         goto fail_nomem_anon_vma_fork;
                 if (tmp->vm_flags & VM_WIPEONFORK) {
                         /*
                          * VM_WIPEONFORK gets a clean slate in the child.
                          * Don't prepare anon_vma until fault since we don't
                          * copy page for current vma.
                          */
                         tmp->anon_vma = NULL;
                 } else if (anon_vma_fork(tmp, mpnt))
                         goto fail_nomem_anon_vma_fork;
                 vm_flags_clear(tmp, VM_LOCKED_MASK);
                 /*
                  * Copy/update hugetlb private vma information.
                  */
                 if (is_vm_hugetlb_page(tmp))
                         hugetlb_dup_vma_private(tmp);
 
                 /*
                  * Link the vma into the MT. After using __mt_dup(), memory
                  * allocation is not necessary here, so it cannot fail.
                  */
                 vma_iter_bulk_store(&vmi, tmp);
 
                 mm->map_count++;
 
                 if (tmp->vm_ops && tmp->vm_ops->open)
                         tmp->vm_ops->open(tmp);
 
                 file = tmp->vm_file;
                 if (file) {
                         struct address_space *mapping = file->f_mapping;
 
                         get_file(file);
                         i_mmap_lock_write(mapping);
                         if (vma_is_shared_maywrite(tmp))
                                 mapping_allow_writable(mapping);
                         flush_dcache_mmap_lock(mapping);
                         /* insert tmp into the share list, just after mpnt */
                         vma_interval_tree_insert_after(tmp, mpnt,
                                         &mapping->i_mmap);
                         flush_dcache_mmap_unlock(mapping);
                         i_mmap_unlock_write(mapping);
                 }
 
                 if (!(tmp->vm_flags & VM_WIPEONFORK))
                         retval = copy_page_range(tmp, mpnt);
 
                 if (retval) {
                         mpnt = vma_next(&vmi);
                         goto loop_out;
                 }
         }
         /* a new mm has just been created */
         retval = arch_dup_mmap(oldmm, mm);
 loop_out:
         vma_iter_free(&vmi);
         if (!retval) {
                 mt_set_in_rcu(vmi.mas.tree);
         } else if (mpnt) {
                 /*
                  * The entire maple tree has already been duplicated. If the
                  * mmap duplication fails, mark the failure point with
                  * XA_ZERO_ENTRY. In exit_mmap(), if this marker is encountered,
                  * stop releasing VMAs that have not been duplicated after this
                  * point.
                  */
                 mas_set_range(&vmi.mas, mpnt->vm_start, mpnt->vm_end - 1);
                 mas_store(&vmi.mas, XA_ZERO_ENTRY);
         }
 out:
         mmap_write_unlock(mm);
         flush_tlb_mm(oldmm);
         mmap_write_unlock(oldmm);
         dup_userfaultfd_complete(&uf);
 fail_uprobe_end:
         uprobe_end_dup_mmap();
         return retval;
 
 fail_nomem_anon_vma_fork:
         mpol_put(vma_policy(tmp));
 fail_nomem_policy:
         vm_area_free(tmp);
 fail_nomem:
         retval = -ENOMEM;
         vm_unacct_memory(charge);
         goto loop_out;
 }
 
 static inline int mm_alloc_pgd(struct mm_struct *mm)
 {
         mm->pgd = pgd_alloc(mm);
         if (unlikely(!mm->pgd))
                 return -ENOMEM;
         return 0;
 }
 
 static inline void mm_free_pgd(struct mm_struct *mm)
 {
         pgd_free(mm, mm->pgd);
 }
 #else
 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 {
         mmap_write_lock(oldmm);
         dup_mm_exe_file(mm, oldmm);
         mmap_write_unlock(oldmm);
         return 0;
 }
 #define mm_alloc_pgd(mm)        (0)
 #define mm_free_pgd(mm)
 #endif /* CONFIG_MMU */
 
 static void check_mm(struct mm_struct *mm)
 {
         int i;
 
         BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
                          "Please make sure 'struct resident_page_types[]' is updated as well");
 
         for (i = 0; i < NR_MM_COUNTERS; i++) {
                 long x = percpu_counter_sum(&mm->rss_stat[i]);
 
                 if (unlikely(x))
                         pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
                                  mm, resident_page_types[i], x);
         }
 
         if (mm_pgtables_bytes(mm))
                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
                                 mm_pgtables_bytes(mm));
 
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 #endif
 }
 
 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 
 static void do_check_lazy_tlb(void *arg)
 {
         struct mm_struct *mm = arg;
 
         WARN_ON_ONCE(current->active_mm == mm);
 }
 
 static void do_shoot_lazy_tlb(void *arg)
 {
         struct mm_struct *mm = arg;
 
         if (current->active_mm == mm) {
                 WARN_ON_ONCE(current->mm);
                 current->active_mm = &init_mm;
                 switch_mm(mm, &init_mm, current);
         }
 }
 
 static void cleanup_lazy_tlbs(struct mm_struct *mm)
 {
         if (!IS_ENABLED(CONFIG_MMU_LAZY_TLB_SHOOTDOWN)) {
                 /*
                  * In this case, lazy tlb mms are refounted and would not reach
                  * __mmdrop until all CPUs have switched away and mmdrop()ed.
                  */
                 return;
         }
 
         /*
          * Lazy mm shootdown does not refcount "lazy tlb mm" usage, rather it
          * requires lazy mm users to switch to another mm when the refcount
          * drops to zero, before the mm is freed. This requires IPIs here to
          * switch kernel threads to init_mm.
          *
          * archs that use IPIs to flush TLBs can piggy-back that lazy tlb mm
          * switch with the final userspace teardown TLB flush which leaves the
          * mm lazy on this CPU but no others, reducing the need for additional
          * IPIs here. There are cases where a final IPI is still required here,
          * such as the final mmdrop being performed on a different CPU than the
          * one exiting, or kernel threads using the mm when userspace exits.
          *
          * IPI overheads have not found to be expensive, but they could be
          * reduced in a number of possible ways, for example (roughly
          * increasing order of complexity):
          * - The last lazy reference created by exit_mm() could instead switch
          *   to init_mm, however it's probable this will run on the same CPU
          *   immediately afterwards, so this may not reduce IPIs much.
          * - A batch of mms requiring IPIs could be gathered and freed at once.
          * - CPUs store active_mm where it can be remotely checked without a
          *   lock, to filter out false-positives in the cpumask.
          * - After mm_users or mm_count reaches zero, switching away from the
          *   mm could clear mm_cpumask to reduce some IPIs, perhaps together
          *   with some batching or delaying of the final IPIs.
          * - A delayed freeing and RCU-like quiescing sequence based on mm
          *   switching to avoid IPIs completely.
          */
         on_each_cpu_mask(mm_cpumask(mm), do_shoot_lazy_tlb, (void *)mm, 1);
         if (IS_ENABLED(CONFIG_DEBUG_VM_SHOOT_LAZIES))
                 on_each_cpu(do_check_lazy_tlb, (void *)mm, 1);
 }
 
 /*
  * Called when the last reference to the mm
  * is dropped: either by a lazy thread or by
  * mmput. Free the page directory and the mm.
  */
 void __mmdrop(struct mm_struct *mm)
 {
         BUG_ON(mm == &init_mm);
         WARN_ON_ONCE(mm == current->mm);
 
         /* Ensure no CPUs are using this as their lazy tlb mm */
         cleanup_lazy_tlbs(mm);
 
         WARN_ON_ONCE(mm == current->active_mm);
         mm_free_pgd(mm);
         destroy_context(mm);
         mmu_notifier_subscriptions_destroy(mm);
         check_mm(mm);
         put_user_ns(mm->user_ns);
         mm_pasid_drop(mm);
         mm_destroy_cid(mm);
         percpu_counter_destroy_many(mm->rss_stat, NR_MM_COUNTERS);
 
         free_mm(mm);
 }
 EXPORT_SYMBOL_GPL(__mmdrop);
 
 static void mmdrop_async_fn(struct work_struct *work)
 {
         struct mm_struct *mm;
 
         mm = container_of(work, struct mm_struct, async_put_work);
         __mmdrop(mm);
 }
 
 static void mmdrop_async(struct mm_struct *mm)
 {
         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
                 schedule_work(&mm->async_put_work);
         }
 }
 
 static inline void free_signal_struct(struct signal_struct *sig)
 {
         taskstats_tgid_free(sig);
         sched_autogroup_exit(sig);
         /*
          * __mmdrop is not safe to call from softirq context on x86 due to
          * pgd_dtor so postpone it to the async context
          */
         if (sig->oom_mm)
                 mmdrop_async(sig->oom_mm);
         kmem_cache_free(signal_cachep, sig);
 }
 
 static inline void put_signal_struct(struct signal_struct *sig)
 {
         if (refcount_dec_and_test(&sig->sigcnt))
                 free_signal_struct(sig);
 }
 
 void __put_task_struct(struct task_struct *tsk)
 {
         WARN_ON(!tsk->exit_state);
         WARN_ON(refcount_read(&tsk->usage));
         WARN_ON(tsk == current);
 
         io_uring_free(tsk);
         cgroup_free(tsk);
         task_numa_free(tsk, true);
         security_task_free(tsk);
         exit_creds(tsk);
         delayacct_tsk_free(tsk);
         put_signal_struct(tsk->signal);
         sched_core_free(tsk);
         free_task(tsk);
 }
 EXPORT_SYMBOL_GPL(__put_task_struct);
 
 void __put_task_struct_rcu_cb(struct rcu_head *rhp)
 {
         struct task_struct *task = container_of(rhp, struct task_struct, rcu);
 
         __put_task_struct(task);
 }
 EXPORT_SYMBOL_GPL(__put_task_struct_rcu_cb);
 
 void __init __weak arch_task_cache_init(void) { }
 
 /*
  * set_max_threads
  */
 static void __init set_max_threads(unsigned int max_threads_suggested)
 {
         u64 threads;
         unsigned long nr_pages = PHYS_PFN(memblock_phys_mem_size() - memblock_reserved_size());
 
         /*
          * The number of threads shall be limited such that the thread
          * structures may only consume a small part of the available memory.
          */
         if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
                 threads = MAX_THREADS;
         else
                 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
                                     (u64) THREAD_SIZE * 8UL);
 
         if (threads > max_threads_suggested)
                 threads = max_threads_suggested;
 
         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 }
 
 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 /* Initialized by the architecture: */
 int arch_task_struct_size __read_mostly;
 #endif
 
 static void __init task_struct_whitelist(unsigned long *offset, unsigned long *size)
 {
         /* Fetch thread_struct whitelist for the architecture. */
         arch_thread_struct_whitelist(offset, size);
 
         /*
          * Handle zero-sized whitelist or empty thread_struct, otherwise
          * adjust offset to position of thread_struct in task_struct.
          */
         if (unlikely(*size == 0))
                 *offset = 0;
         else
                 *offset += offsetof(struct task_struct, thread);
 }
 
 void __init fork_init(void)
 {
         int i;
 #ifndef ARCH_MIN_TASKALIGN
 #define ARCH_MIN_TASKALIGN      0
 #endif
         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
         unsigned long useroffset, usersize;
 
         /* create a slab on which task_structs can be allocated */
         task_struct_whitelist(&useroffset, &usersize);
         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
                         arch_task_struct_size, align,
                         SLAB_PANIC|SLAB_ACCOUNT,
                         useroffset, usersize, NULL);
 
         /* do the arch specific task caches init */
         arch_task_cache_init();
 
         set_max_threads(MAX_THREADS);
 
         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
         init_task.signal->rlim[RLIMIT_SIGPENDING] =
                 init_task.signal->rlim[RLIMIT_NPROC];
 
         for (i = 0; i < UCOUNT_COUNTS; i++)
                 init_user_ns.ucount_max[i] = max_threads/2;
 
         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,      RLIM_INFINITY);
         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,   RLIM_INFINITY);
         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,    RLIM_INFINITY);
 
 #ifdef CONFIG_VMAP_STACK
         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
                           NULL, free_vm_stack_cache);
 #endif
 
         scs_init();
 
         lockdep_init_task(&init_task);
         uprobes_init();
 }
 
 int __weak arch_dup_task_struct(struct task_struct *dst,
                                                struct task_struct *src)
 {
         *dst = *src;
         return 0;
 }
 
 void set_task_stack_end_magic(struct task_struct *tsk)
 {
         unsigned long *stackend;
 
         stackend = end_of_stack(tsk);
         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 }
 
 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 {
         struct task_struct *tsk;
         int err;
 
         if (node == NUMA_NO_NODE)
                 node = tsk_fork_get_node(orig);
         tsk = alloc_task_struct_node(node);
         if (!tsk)
                 return NULL;
 
         err = arch_dup_task_struct(tsk, orig);
         if (err)
                 goto free_tsk;
 
         err = alloc_thread_stack_node(tsk, node);
         if (err)
                 goto free_tsk;
 
 #ifdef CONFIG_THREAD_INFO_IN_TASK
         refcount_set(&tsk->stack_refcount, 1);
 #endif
         account_kernel_stack(tsk, 1);
 
         err = scs_prepare(tsk, node);
         if (err)
                 goto free_stack;
 
 #ifdef CONFIG_SECCOMP
         /*
          * We must handle setting up seccomp filters once we're under
          * the sighand lock in case orig has changed between now and
          * then. Until then, filter must be NULL to avoid messing up
          * the usage counts on the error path calling free_task.
          */
         tsk->seccomp.filter = NULL;
 #endif
 
         setup_thread_stack(tsk, orig);
         clear_user_return_notifier(tsk);
         clear_tsk_need_resched(tsk);
         set_task_stack_end_magic(tsk);
         clear_syscall_work_syscall_user_dispatch(tsk);
 
 #ifdef CONFIG_STACKPROTECTOR
         tsk->stack_canary = get_random_canary();
 #endif
         if (orig->cpus_ptr == &orig->cpus_mask)
                 tsk->cpus_ptr = &tsk->cpus_mask;
         dup_user_cpus_ptr(tsk, orig, node);
 
         /*
          * One for the user space visible state that goes away when reaped.
          * One for the scheduler.
          */
         refcount_set(&tsk->rcu_users, 2);
         /* One for the rcu users */
         refcount_set(&tsk->usage, 1);
 #ifdef CONFIG_BLK_DEV_IO_TRACE
         tsk->btrace_seq = 0;
 #endif
         tsk->splice_pipe = NULL;
         tsk->task_frag.page = NULL;
         tsk->wake_q.next = NULL;
         tsk->worker_private = NULL;
 
         kcov_task_init(tsk);
         kmsan_task_create(tsk);
         kmap_local_fork(tsk);
 
 #ifdef CONFIG_FAULT_INJECTION
         tsk->fail_nth = 0;
 #endif
 
 #ifdef CONFIG_BLK_CGROUP
         tsk->throttle_disk = NULL;
         tsk->use_memdelay = 0;
 #endif
 
 #ifdef CONFIG_ARCH_HAS_CPU_PASID
         tsk->pasid_activated = 0;
 #endif
 
 #ifdef CONFIG_MEMCG
         tsk->active_memcg = NULL;
 #endif
 
 #ifdef CONFIG_CPU_SUP_INTEL
         tsk->reported_split_lock = 0;
 #endif
 
 #ifdef CONFIG_SCHED_MM_CID
         tsk->mm_cid = -1;
         tsk->last_mm_cid = -1;
         tsk->mm_cid_active = 0;
         tsk->migrate_from_cpu = -1;
 #endif
         return tsk;
 
 free_stack:
         exit_task_stack_account(tsk);
         free_thread_stack(tsk);
 free_tsk:
         free_task_struct(tsk);
         return NULL;
 }
 
 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 
 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 
 static int __init coredump_filter_setup(char *s)
 {
         default_dump_filter =
                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
                 MMF_DUMP_FILTER_MASK;
         return 1;
 }
 
 __setup("coredump_filter=", coredump_filter_setup);
 
 #include <linux/init_task.h>
 
 static void mm_init_aio(struct mm_struct *mm)
 {
 #ifdef CONFIG_AIO
         spin_lock_init(&mm->ioctx_lock);
         mm->ioctx_table = NULL;
 #endif
 }
 
 static __always_inline void mm_clear_owner(struct mm_struct *mm,
                                            struct task_struct *p)
 {
 #ifdef CONFIG_MEMCG
         if (mm->owner == p)
                 WRITE_ONCE(mm->owner, NULL);
 #endif
 }
 
 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 {
 #ifdef CONFIG_MEMCG
         mm->owner = p;
 #endif
 }
 
 static void mm_init_uprobes_state(struct mm_struct *mm)
 {
 #ifdef CONFIG_UPROBES
         mm->uprobes_state.xol_area = NULL;
 #endif
 }
 
 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
         struct user_namespace *user_ns)
 {
         mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
         mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
         atomic_set(&mm->mm_users, 1);
         atomic_set(&mm->mm_count, 1);
         seqcount_init(&mm->write_protect_seq);
         mmap_init_lock(mm);
         INIT_LIST_HEAD(&mm->mmlist);
 #ifdef CONFIG_PER_VMA_LOCK
         mm->mm_lock_seq = 0;
 #endif
         mm_pgtables_bytes_init(mm);
         mm->map_count = 0;
         mm->locked_vm = 0;
         atomic64_set(&mm->pinned_vm, 0);
         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
         spin_lock_init(&mm->page_table_lock);
         spin_lock_init(&mm->arg_lock);
         mm_init_cpumask(mm);
         mm_init_aio(mm);
         mm_init_owner(mm, p);
         mm_pasid_init(mm);
         RCU_INIT_POINTER(mm->exe_file, NULL);
         mmu_notifier_subscriptions_init(mm);
         init_tlb_flush_pending(mm);
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
         mm->pmd_huge_pte = NULL;
 #endif
         mm_init_uprobes_state(mm);
         hugetlb_count_init(mm);
 
         if (current->mm) {
                 mm->flags = mmf_init_flags(current->mm->flags);
                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
         } else {
                 mm->flags = default_dump_filter;
                 mm->def_flags = 0;
         }
 
         if (mm_alloc_pgd(mm))
                 goto fail_nopgd;
 
         if (init_new_context(p, mm))
                 goto fail_nocontext;
 
         if (mm_alloc_cid(mm))
                 goto fail_cid;
 
         if (percpu_counter_init_many(mm->rss_stat, 0, GFP_KERNEL_ACCOUNT,
                                      NR_MM_COUNTERS))
                 goto fail_pcpu;
 
         mm->user_ns = get_user_ns(user_ns);
         lru_gen_init_mm(mm);
         return mm;
 
 fail_pcpu:
         mm_destroy_cid(mm);
 fail_cid:
         destroy_context(mm);
 fail_nocontext:
         mm_free_pgd(mm);
 fail_nopgd:
         free_mm(mm);
         return NULL;
 }
 
 /*
  * Allocate and initialize an mm_struct.
  */
 struct mm_struct *mm_alloc(void)
 {
         struct mm_struct *mm;
 
         mm = allocate_mm();
         if (!mm)
                 return NULL;
 
         memset(mm, 0, sizeof(*mm));
         return mm_init(mm, current, current_user_ns());
 }
 EXPORT_SYMBOL_IF_KUNIT(mm_alloc);
 
 static inline void __mmput(struct mm_struct *mm)
 {
         VM_BUG_ON(atomic_read(&mm->mm_users));
 
         uprobe_clear_state(mm);
         exit_aio(mm);
         ksm_exit(mm);
         khugepaged_exit(mm); /* must run before exit_mmap */
         exit_mmap(mm);
         mm_put_huge_zero_folio(mm);
         set_mm_exe_file(mm, NULL);
         if (!list_empty(&mm->mmlist)) {
                 spin_lock(&mmlist_lock);
                 list_del(&mm->mmlist);
                 spin_unlock(&mmlist_lock);
         }
         if (mm->binfmt)
                 module_put(mm->binfmt->module);
         lru_gen_del_mm(mm);
         mmdrop(mm);
 }
 
 /*
  * Decrement the use count and release all resources for an mm.
  */
 void mmput(struct mm_struct *mm)
 {
         might_sleep();
 
         if (atomic_dec_and_test(&mm->mm_users))
                 __mmput(mm);
 }
 EXPORT_SYMBOL_GPL(mmput);
 
 #ifdef CONFIG_MMU
 static void mmput_async_fn(struct work_struct *work)
 {
         struct mm_struct *mm = container_of(work, struct mm_struct,
                                             async_put_work);
 
         __mmput(mm);
 }
 
 void mmput_async(struct mm_struct *mm)
 {
         if (atomic_dec_and_test(&mm->mm_users)) {
                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
                 schedule_work(&mm->async_put_work);
         }
 }
 EXPORT_SYMBOL_GPL(mmput_async);
 #endif
 
 /**
  * set_mm_exe_file - change a reference to the mm's executable file
  * @mm: The mm to change.
  * @new_exe_file: The new file to use.
  *
  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
  *
  * Main users are mmput() and sys_execve(). Callers prevent concurrent
  * invocations: in mmput() nobody alive left, in execve it happens before
  * the new mm is made visible to anyone.
  *
  * Can only fail if new_exe_file != NULL.
  */
 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 {
         struct file *old_exe_file;
 
         /*
          * It is safe to dereference the exe_file without RCU as
          * this function is only called if nobody else can access
          * this mm -- see comment above for justification.
          */
         old_exe_file = rcu_dereference_raw(mm->exe_file);
 
         if (new_exe_file)
                 get_file(new_exe_file);
         rcu_assign_pointer(mm->exe_file, new_exe_file);
         if (old_exe_file)
                 fput(old_exe_file);
         return 0;
 }
 
 /**
  * replace_mm_exe_file - replace a reference to the mm's executable file
  * @mm: The mm to change.
  * @new_exe_file: The new file to use.
  *
  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
  *
  * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
  */
 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 {
         struct vm_area_struct *vma;
         struct file *old_exe_file;
         int ret = 0;
 
         /* Forbid mm->exe_file change if old file still mapped. */
         old_exe_file = get_mm_exe_file(mm);
         if (old_exe_file) {
                 VMA_ITERATOR(vmi, mm, 0);
                 mmap_read_lock(mm);
                 for_each_vma(vmi, vma) {
                         if (!vma->vm_file)
                                 continue;
                         if (path_equal(&vma->vm_file->f_path,
                                        &old_exe_file->f_path)) {
                                 ret = -EBUSY;
                                 break;
                         }
                 }
                 mmap_read_unlock(mm);
                 fput(old_exe_file);
                 if (ret)
                         return ret;
         }
 
         get_file(new_exe_file);
 
         /* set the new file */
         mmap_write_lock(mm);
         old_exe_file = rcu_dereference_raw(mm->exe_file);
         rcu_assign_pointer(mm->exe_file, new_exe_file);
         mmap_write_unlock(mm);
 
         if (old_exe_file)
                 fput(old_exe_file);
         return 0;
 }
 
 /**
  * get_mm_exe_file - acquire a reference to the mm's executable file
  * @mm: The mm of interest.
  *
  * Returns %NULL if mm has no associated executable file.
  * User must release file via fput().
  */
 struct file *get_mm_exe_file(struct mm_struct *mm)
 {
         struct file *exe_file;
 
         rcu_read_lock();
         exe_file = get_file_rcu(&mm->exe_file);
         rcu_read_unlock();
         return exe_file;
 }
 
 /**
  * get_task_exe_file - acquire a reference to the task's executable file
  * @task: The task.
  *
  * Returns %NULL if task's mm (if any) has no associated executable file or
  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
  * User must release file via fput().
  */
 struct file *get_task_exe_file(struct task_struct *task)
 {
         struct file *exe_file = NULL;
         struct mm_struct *mm;
 
         task_lock(task);
         mm = task->mm;
         if (mm) {
                 if (!(task->flags & PF_KTHREAD))
                         exe_file = get_mm_exe_file(mm);
         }
         task_unlock(task);
         return exe_file;
 }
 
 /**
  * get_task_mm - acquire a reference to the task's mm
  * @task: The task.
  *
  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
  * this kernel workthread has transiently adopted a user mm with use_mm,
  * to do its AIO) is not set and if so returns a reference to it, after
  * bumping up the use count.  User must release the mm via mmput()
  * after use.  Typically used by /proc and ptrace.
  */
 struct mm_struct *get_task_mm(struct task_struct *task)
 {
         struct mm_struct *mm;
 
         if (task->flags & PF_KTHREAD)
                 return NULL;
 
         task_lock(task);
         mm = task->mm;
         if (mm)
                 mmget(mm);
         task_unlock(task);
         return mm;
 }
 EXPORT_SYMBOL_GPL(get_task_mm);
 
 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 {
         struct mm_struct *mm;
         int err;
 
         err =  down_read_killable(&task->signal->exec_update_lock);
         if (err)
                 return ERR_PTR(err);
 
         mm = get_task_mm(task);
         if (mm && mm != current->mm &&
                         !ptrace_may_access(task, mode)) {
                 mmput(mm);
                 mm = ERR_PTR(-EACCES);
         }
         up_read(&task->signal->exec_update_lock);
 
         return mm;
 }
 
 static void complete_vfork_done(struct task_struct *tsk)
 {
         struct completion *vfork;
 
         task_lock(tsk);
         vfork = tsk->vfork_done;
         if (likely(vfork)) {
                 tsk->vfork_done = NULL;
                 complete(vfork);
         }
         task_unlock(tsk);
 }
 
 static int wait_for_vfork_done(struct task_struct *child,
                                 struct completion *vfork)
 {
         unsigned int state = TASK_KILLABLE|TASK_FREEZABLE;
         int killed;
 
         cgroup_enter_frozen();
         killed = wait_for_completion_state(vfork, state);
         cgroup_leave_frozen(false);
 
         if (killed) {
                 task_lock(child);
                 child->vfork_done = NULL;
                 task_unlock(child);
         }
 
         put_task_struct(child);
         return killed;
 }
 
 /* Please note the differences between mmput and mm_release.
  * mmput is called whenever we stop holding onto a mm_struct,
  * error success whatever.
  *
  * mm_release is called after a mm_struct has been removed
  * from the current process.
  *
  * This difference is important for error handling, when we
  * only half set up a mm_struct for a new process and need to restore
  * the old one.  Because we mmput the new mm_struct before
  * restoring the old one. . .
  * Eric Biederman 10 January 1998
  */
 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 {
         uprobe_free_utask(tsk);
 
         /* Get rid of any cached register state */
         deactivate_mm(tsk, mm);
 
         /*
          * Signal userspace if we're not exiting with a core dump
          * because we want to leave the value intact for debugging
          * purposes.
          */
         if (tsk->clear_child_tid) {
                 if (atomic_read(&mm->mm_users) > 1) {
                         /*
                          * We don't check the error code - if userspace has
                          * not set up a proper pointer then tough luck.
                          */
                         put_user(0, tsk->clear_child_tid);
                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
                                         1, NULL, NULL, 0, 0);
                 }
                 tsk->clear_child_tid = NULL;
         }
 
         /*
          * All done, finally we can wake up parent and return this mm to him.
          * Also kthread_stop() uses this completion for synchronization.
          */
         if (tsk->vfork_done)
                 complete_vfork_done(tsk);
 }
 
 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
 {
         futex_exit_release(tsk);
         mm_release(tsk, mm);
 }
 
 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
 {
         futex_exec_release(tsk);
         mm_release(tsk, mm);
 }
 
 /**
  * dup_mm() - duplicates an existing mm structure
  * @tsk: the task_struct with which the new mm will be associated.
  * @oldmm: the mm to duplicate.
  *
  * Allocates a new mm structure and duplicates the provided @oldmm structure
  * content into it.
  *
  * Return: the duplicated mm or NULL on failure.
  */
 static struct mm_struct *dup_mm(struct task_struct *tsk,
                                 struct mm_struct *oldmm)
 {
         struct mm_struct *mm;
         int err;
 
         mm = allocate_mm();
         if (!mm)
                 goto fail_nomem;
 
         memcpy(mm, oldmm, sizeof(*mm));
 
         if (!mm_init(mm, tsk, mm->user_ns))
                 goto fail_nomem;
 
         err = dup_mmap(mm, oldmm);
         if (err)
                 goto free_pt;
 
         mm->hiwater_rss = get_mm_rss(mm);
         mm->hiwater_vm = mm->total_vm;
 
         if (mm->binfmt && !try_module_get(mm->binfmt->module))
                 goto free_pt;
 
         return mm;
 
 free_pt:
         /* don't put binfmt in mmput, we haven't got module yet */
         mm->binfmt = NULL;
         mm_init_owner(mm, NULL);
         mmput(mm);
 
 fail_nomem:
         return NULL;
 }
 
 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 {
         struct mm_struct *mm, *oldmm;
 
         tsk->min_flt = tsk->maj_flt = 0;
         tsk->nvcsw = tsk->nivcsw = 0;
 #ifdef CONFIG_DETECT_HUNG_TASK
         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
         tsk->last_switch_time = 0;
 #endif
 
         tsk->mm = NULL;
         tsk->active_mm = NULL;
 
         /*
          * Are we cloning a kernel thread?
          *
          * We need to steal a active VM for that..
          */
         oldmm = current->mm;
         if (!oldmm)
                 return 0;
 
         if (clone_flags & CLONE_VM) {
                 mmget(oldmm);
                 mm = oldmm;
         } else {
                 mm = dup_mm(tsk, current->mm);
                 if (!mm)
                         return -ENOMEM;
         }
 
         tsk->mm = mm;
         tsk->active_mm = mm;
         sched_mm_cid_fork(tsk);
         return 0;
 }
 
 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 {
         struct fs_struct *fs = current->fs;
         if (clone_flags & CLONE_FS) {
                 /* tsk->fs is already what we want */
                 spin_lock(&fs->lock);
                 /* "users" and "in_exec" locked for check_unsafe_exec() */
                 if (fs->in_exec) {
                         spin_unlock(&fs->lock);
                         return -EAGAIN;
                 }
                 fs->users++;
                 spin_unlock(&fs->lock);
                 return 0;
         }
         tsk->fs = copy_fs_struct(fs);
         if (!tsk->fs)
                 return -ENOMEM;
         return 0;
 }
 
 static int copy_files(unsigned long clone_flags, struct task_struct *tsk,
                       int no_files)
 {
         struct files_struct *oldf, *newf;
 
         /*
          * A background process may not have any files ...
          */
         oldf = current->files;
         if (!oldf)
                 return 0;
 
         if (no_files) {
                 tsk->files = NULL;
                 return 0;
         }
 
         if (clone_flags & CLONE_FILES) {
                 atomic_inc(&oldf->count);
                 return 0;
         }
 
         newf = dup_fd(oldf, NULL);
         if (IS_ERR(newf))
                 return PTR_ERR(newf);
 
         tsk->files = newf;
         return 0;
 }
 
 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 {
         struct sighand_struct *sig;
 
         if (clone_flags & CLONE_SIGHAND) {
                 refcount_inc(&current->sighand->count);
                 return 0;
         }
         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
         RCU_INIT_POINTER(tsk->sighand, sig);
         if (!sig)
                 return -ENOMEM;
 
         refcount_set(&sig->count, 1);
         spin_lock_irq(&current->sighand->siglock);
         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
         spin_unlock_irq(&current->sighand->siglock);
 
         /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
         if (clone_flags & CLONE_CLEAR_SIGHAND)
                 flush_signal_handlers(tsk, 0);
 
         return 0;
 }
 
 void __cleanup_sighand(struct sighand_struct *sighand)
 {
         if (refcount_dec_and_test(&sighand->count)) {
                 signalfd_cleanup(sighand);
                 /*
                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
                  * without an RCU grace period, see __lock_task_sighand().
                  */
                 kmem_cache_free(sighand_cachep, sighand);
         }
 }
 
 /*
  * Initialize POSIX timer handling for a thread group.
  */
 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 {
         struct posix_cputimers *pct = &sig->posix_cputimers;
         unsigned long cpu_limit;
 
         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
         posix_cputimers_group_init(pct, cpu_limit);
 }
 
 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 {
         struct signal_struct *sig;
 
         if (clone_flags & CLONE_THREAD)
                 return 0;
 
         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
         tsk->signal = sig;
         if (!sig)
                 return -ENOMEM;
 
         sig->nr_threads = 1;
         sig->quick_threads = 1;
         atomic_set(&sig->live, 1);
         refcount_set(&sig->sigcnt, 1);
 
         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
 
         init_waitqueue_head(&sig->wait_chldexit);
         sig->curr_target = tsk;
         init_sigpending(&sig->shared_pending);
         INIT_HLIST_HEAD(&sig->multiprocess);
         seqlock_init(&sig->stats_lock);
         prev_cputime_init(&sig->prev_cputime);
 
 #ifdef CONFIG_POSIX_TIMERS
         INIT_LIST_HEAD(&sig->posix_timers);
         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         sig->real_timer.function = it_real_fn;
 #endif
 
         task_lock(current->group_leader);
         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
         task_unlock(current->group_leader);
 
         posix_cpu_timers_init_group(sig);
 
         tty_audit_fork(sig);
         sched_autogroup_fork(sig);
 
         sig->oom_score_adj = current->signal->oom_score_adj;
         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 
         mutex_init(&sig->cred_guard_mutex);
         init_rwsem(&sig->exec_update_lock);
 
         return 0;
 }
 
 static void copy_seccomp(struct task_struct *p)
 {
 #ifdef CONFIG_SECCOMP
         /*
          * Must be called with sighand->lock held, which is common to
          * all threads in the group. Holding cred_guard_mutex is not
          * needed because this new task is not yet running and cannot
          * be racing exec.
          */
         assert_spin_locked(&current->sighand->siglock);
 
         /* Ref-count the new filter user, and assign it. */
         get_seccomp_filter(current);
         p->seccomp = current->seccomp;
 
         /*
          * Explicitly enable no_new_privs here in case it got set
          * between the task_struct being duplicated and holding the
          * sighand lock. The seccomp state and nnp must be in sync.
          */
         if (task_no_new_privs(current))
                 task_set_no_new_privs(p);
 
         /*
          * If the parent gained a seccomp mode after copying thread
          * flags and between before we held the sighand lock, we have
          * to manually enable the seccomp thread flag here.
          */
         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
                 set_task_syscall_work(p, SECCOMP);
 #endif
 }
 
 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 {
         current->clear_child_tid = tidptr;
 
         return task_pid_vnr(current);
 }
 
 static void rt_mutex_init_task(struct task_struct *p)
 {
         raw_spin_lock_init(&p->pi_lock);
 #ifdef CONFIG_RT_MUTEXES
         p->pi_waiters = RB_ROOT_CACHED;
         p->pi_top_task = NULL;
         p->pi_blocked_on = NULL;
 #endif
 }
 
 static inline void init_task_pid_links(struct task_struct *task)
 {
         enum pid_type type;
 
         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
                 INIT_HLIST_NODE(&task->pid_links[type]);
 }
 
 static inline void
 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
 {
         if (type == PIDTYPE_PID)
                 task->thread_pid = pid;
         else
                 task->signal->pids[type] = pid;
 }
 
 static inline void rcu_copy_process(struct task_struct *p)
 {
 #ifdef CONFIG_PREEMPT_RCU
         p->rcu_read_lock_nesting = 0;
         p->rcu_read_unlock_special.s = 0;
         p->rcu_blocked_node = NULL;
         INIT_LIST_HEAD(&p->rcu_node_entry);
 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 #ifdef CONFIG_TASKS_RCU
         p->rcu_tasks_holdout = false;
         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
         p->rcu_tasks_idle_cpu = -1;
         INIT_LIST_HEAD(&p->rcu_tasks_exit_list);
 #endif /* #ifdef CONFIG_TASKS_RCU */
 #ifdef CONFIG_TASKS_TRACE_RCU
         p->trc_reader_nesting = 0;
         p->trc_reader_special.s = 0;
         INIT_LIST_HEAD(&p->trc_holdout_list);
         INIT_LIST_HEAD(&p->trc_blkd_node);
 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
 }
 
 /**
  * __pidfd_prepare - allocate a new pidfd_file and reserve a pidfd
  * @pid:   the struct pid for which to create a pidfd
  * @flags: flags of the new @pidfd
  * @ret: Where to return the file for the pidfd.
  *
  * Allocate a new file that stashes @pid and reserve a new pidfd number in the
  * caller's file descriptor table. The pidfd is reserved but not installed yet.
  *
  * The helper doesn't perform checks on @pid which makes it useful for pidfds
  * created via CLONE_PIDFD where @pid has no task attached when the pidfd and
  * pidfd file are prepared.
  *
  * If this function returns successfully the caller is responsible to either
  * call fd_install() passing the returned pidfd and pidfd file as arguments in
  * order to install the pidfd into its file descriptor table or they must use
  * put_unused_fd() and fput() on the returned pidfd and pidfd file
  * respectively.
  *
  * This function is useful when a pidfd must already be reserved but there
  * might still be points of failure afterwards and the caller wants to ensure
  * that no pidfd is leaked into its file descriptor table.
  *
  * Return: On success, a reserved pidfd is returned from the function and a new
  *         pidfd file is returned in the last argument to the function. On
  *         error, a negative error code is returned from the function and the
  *         last argument remains unchanged.
  */
 static int __pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret)
 {
         int pidfd;
         struct file *pidfd_file;
 
         pidfd = get_unused_fd_flags(O_CLOEXEC);
         if (pidfd < 0)
                 return pidfd;
 
         pidfd_file = pidfs_alloc_file(pid, flags | O_RDWR);
         if (IS_ERR(pidfd_file)) {
                 put_unused_fd(pidfd);
                 return PTR_ERR(pidfd_file);
         }
         /*
          * anon_inode_getfile() ignores everything outside of the
          * O_ACCMODE | O_NONBLOCK mask, set PIDFD_THREAD manually.
          */
         pidfd_file->f_flags |= (flags & PIDFD_THREAD);
         *ret = pidfd_file;
         return pidfd;
 }
 
 /**
  * pidfd_prepare - allocate a new pidfd_file and reserve a pidfd
  * @pid:   the struct pid for which to create a pidfd
  * @flags: flags of the new @pidfd
  * @ret: Where to return the pidfd.
  *
  * Allocate a new file that stashes @pid and reserve a new pidfd number in the
  * caller's file descriptor table. The pidfd is reserved but not installed yet.
  *
  * The helper verifies that @pid is still in use, without PIDFD_THREAD the
  * task identified by @pid must be a thread-group leader.
  *
  * If this function returns successfully the caller is responsible to either
  * call fd_install() passing the returned pidfd and pidfd file as arguments in
  * order to install the pidfd into its file descriptor table or they must use
  * put_unused_fd() and fput() on the returned pidfd and pidfd file
  * respectively.
  *
  * This function is useful when a pidfd must already be reserved but there
  * might still be points of failure afterwards and the caller wants to ensure
  * that no pidfd is leaked into its file descriptor table.
  *
  * Return: On success, a reserved pidfd is returned from the function and a new
  *         pidfd file is returned in the last argument to the function. On
  *         error, a negative error code is returned from the function and the
  *         last argument remains unchanged.
  */
 int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret)
 {
         bool thread = flags & PIDFD_THREAD;
 
         if (!pid || !pid_has_task(pid, thread ? PIDTYPE_PID : PIDTYPE_TGID))
                 return -EINVAL;
 
         return __pidfd_prepare(pid, flags, ret);
 }
 
 static void __delayed_free_task(struct rcu_head *rhp)
 {
         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 
         free_task(tsk);
 }
 
 static __always_inline void delayed_free_task(struct task_struct *tsk)
 {
         if (IS_ENABLED(CONFIG_MEMCG))
                 call_rcu(&tsk->rcu, __delayed_free_task);
         else
                 free_task(tsk);
 }
 
 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
 {
         /* Skip if kernel thread */
         if (!tsk->mm)
                 return;
 
         /* Skip if spawning a thread or using vfork */
         if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
                 return;
 
         /* We need to synchronize with __set_oom_adj */
         mutex_lock(&oom_adj_mutex);
         set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
         /* Update the values in case they were changed after copy_signal */
         tsk->signal->oom_score_adj = current->signal->oom_score_adj;
         tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
         mutex_unlock(&oom_adj_mutex);
 }
 
 #ifdef CONFIG_RV
 static void rv_task_fork(struct task_struct *p)
 {
         int i;
 
         for (i = 0; i < RV_PER_TASK_MONITORS; i++)
                 p->rv[i].da_mon.monitoring = false;
 }
 #else
 #define rv_task_fork(p) do {} while (0)
 #endif
 
 /*
  * This creates a new process as a copy of the old one,
  * but does not actually start it yet.
  *
  * It copies the registers, and all the appropriate
  * parts of the process environment (as per the clone
  * flags). The actual kick-off is left to the caller.
  */
 __latent_entropy struct task_struct *copy_process(
                                         struct pid *pid,
                                         int trace,
                                         int node,
                                         struct kernel_clone_args *args)
 {
         int pidfd = -1, retval;
         struct task_struct *p;
         struct multiprocess_signals delayed;
         struct file *pidfile = NULL;
         const u64 clone_flags = args->flags;
         struct nsproxy *nsp = current->nsproxy;
 
         /*
          * Don't allow sharing the root directory with processes in a different
          * namespace
          */
         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
                 return ERR_PTR(-EINVAL);
 
         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
                 return ERR_PTR(-EINVAL);
 
         /*
          * Thread groups must share signals as well, and detached threads
          * can only be started up within the thread group.
          */
         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
                 return ERR_PTR(-EINVAL);
 
         /*
          * Shared signal handlers imply shared VM. By way of the above,
          * thread groups also imply shared VM. Blocking this case allows
          * for various simplifications in other code.
          */
         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
                 return ERR_PTR(-EINVAL);
 
         /*
          * Siblings of global init remain as zombies on exit since they are
          * not reaped by their parent (swapper). To solve this and to avoid
          * multi-rooted process trees, prevent global and container-inits
          * from creating siblings.
          */
         if ((clone_flags & CLONE_PARENT) &&
                                 current->signal->flags & SIGNAL_UNKILLABLE)
                 return ERR_PTR(-EINVAL);
 
         /*
          * If the new process will be in a different pid or user namespace
          * do not allow it to share a thread group with the forking task.
          */
         if (clone_flags & CLONE_THREAD) {
                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
                     (task_active_pid_ns(current) != nsp->pid_ns_for_children))
                         return ERR_PTR(-EINVAL);
         }
 
         if (clone_flags & CLONE_PIDFD) {
                 /*
                  * - CLONE_DETACHED is blocked so that we can potentially
                  *   reuse it later for CLONE_PIDFD.
                  */
                 if (clone_flags & CLONE_DETACHED)
                         return ERR_PTR(-EINVAL);
         }
 
         /*
          * Force any signals received before this point to be delivered
          * before the fork happens.  Collect up signals sent to multiple
          * processes that happen during the fork and delay them so that
          * they appear to happen after the fork.
          */
         sigemptyset(&delayed.signal);
         INIT_HLIST_NODE(&delayed.node);
 
         spin_lock_irq(&current->sighand->siglock);
         if (!(clone_flags & CLONE_THREAD))
                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
         retval = -ERESTARTNOINTR;
         if (task_sigpending(current))
                 goto fork_out;
 
         retval = -ENOMEM;
         p = dup_task_struct(current, node);
         if (!p)
                 goto fork_out;
         p->flags &= ~PF_KTHREAD;
         if (args->kthread)
                 p->flags |= PF_KTHREAD;
         if (args->user_worker) {
                 /*
                  * Mark us a user worker, and block any signal that isn't
                  * fatal or STOP
                  */
                 p->flags |= PF_USER_WORKER;
                 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
         }
         if (args->io_thread)
                 p->flags |= PF_IO_WORKER;
 
         if (args->name)
                 strscpy_pad(p->comm, args->name, sizeof(p->comm));
 
         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
         /*
          * Clear TID on mm_release()?
          */
         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
 
         ftrace_graph_init_task(p);
 
         rt_mutex_init_task(p);
 
         lockdep_assert_irqs_enabled();
 #ifdef CONFIG_PROVE_LOCKING
         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 #endif
         retval = copy_creds(p, clone_flags);
         if (retval < 0)
                 goto bad_fork_free;
 
         retval = -EAGAIN;
         if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
                 if (p->real_cred->user != INIT_USER &&
                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
                         goto bad_fork_cleanup_count;
         }
         current->flags &= ~PF_NPROC_EXCEEDED;
 
         /*
          * If multiple threads are within copy_process(), then this check
          * triggers too late. This doesn't hurt, the check is only there
          * to stop root fork bombs.
          */
         retval = -EAGAIN;
         if (data_race(nr_threads >= max_threads))
                 goto bad_fork_cleanup_count;
 
         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
         p->flags |= PF_FORKNOEXEC;
         INIT_LIST_HEAD(&p->children);
         INIT_LIST_HEAD(&p->sibling);
         rcu_copy_process(p);
         p->vfork_done = NULL;
         spin_lock_init(&p->alloc_lock);
 
         init_sigpending(&p->pending);
 
         p->utime = p->stime = p->gtime = 0;
 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
         p->utimescaled = p->stimescaled = 0;
 #endif
         prev_cputime_init(&p->prev_cputime);
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
         seqcount_init(&p->vtime.seqcount);
         p->vtime.starttime = 0;
         p->vtime.state = VTIME_INACTIVE;
 #endif
 
 #ifdef CONFIG_IO_URING
         p->io_uring = NULL;
 #endif
 
         p->default_timer_slack_ns = current->timer_slack_ns;
 
 #ifdef CONFIG_PSI
         p->psi_flags = 0;
 #endif
 
         task_io_accounting_init(&p->ioac);
         acct_clear_integrals(p);
 
         posix_cputimers_init(&p->posix_cputimers);
 
         p->io_context = NULL;
         audit_set_context(p, NULL);
         cgroup_fork(p);
         if (args->kthread) {
                 if (!set_kthread_struct(p))
                         goto bad_fork_cleanup_delayacct;
         }
 #ifdef CONFIG_NUMA
         p->mempolicy = mpol_dup(p->mempolicy);
         if (IS_ERR(p->mempolicy)) {
                 retval = PTR_ERR(p->mempolicy);
                 p->mempolicy = NULL;
                 goto bad_fork_cleanup_delayacct;
         }
 #endif
 #ifdef CONFIG_CPUSETS
         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
         seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
 #endif
 #ifdef CONFIG_TRACE_IRQFLAGS
         memset(&p->irqtrace, 0, sizeof(p->irqtrace));
         p->irqtrace.hardirq_disable_ip  = _THIS_IP_;
         p->irqtrace.softirq_enable_ip   = _THIS_IP_;
         p->softirqs_enabled             = 1;
         p->softirq_context              = 0;
 #endif
 
         p->pagefault_disabled = 0;
 
 #ifdef CONFIG_LOCKDEP
         lockdep_init_task(p);
 #endif
 
 #ifdef CONFIG_DEBUG_MUTEXES
         p->blocked_on = NULL; /* not blocked yet */
 #endif
 #ifdef CONFIG_BCACHE
         p->sequential_io        = 0;
         p->sequential_io_avg    = 0;
 #endif
 #ifdef CONFIG_BPF_SYSCALL
         RCU_INIT_POINTER(p->bpf_storage, NULL);
         p->bpf_ctx = NULL;
 #endif
 
         /* Perform scheduler related setup. Assign this task to a CPU. */
         retval = sched_fork(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_policy;
 
         retval = perf_event_init_task(p, clone_flags);
         if (retval)
                 goto bad_fork_cleanup_policy;
         retval = audit_alloc(p);
         if (retval)
                 goto bad_fork_cleanup_perf;
         /* copy all the process information */
         shm_init_task(p);
         retval = security_task_alloc(p, clone_flags);
         if (retval)
                 goto bad_fork_cleanup_audit;
         retval = copy_semundo(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_security;
         retval = copy_files(clone_flags, p, args->no_files);
         if (retval)
                 goto bad_fork_cleanup_semundo;
         retval = copy_fs(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_files;
         retval = copy_sighand(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_fs;
         retval = copy_signal(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_sighand;
         retval = copy_mm(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_signal;
         retval = copy_namespaces(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_mm;
         retval = copy_io(clone_flags, p);
         if (retval)
                 goto bad_fork_cleanup_namespaces;
         retval = copy_thread(p, args);
         if (retval)
                 goto bad_fork_cleanup_io;
 
         stackleak_task_init(p);
 
         if (pid != &init_struct_pid) {
                 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
                                 args->set_tid_size);
                 if (IS_ERR(pid)) {
                         retval = PTR_ERR(pid);
                         goto bad_fork_cleanup_thread;
                 }
         }
 
         /*
          * This has to happen after we've potentially unshared the file
          * descriptor table (so that the pidfd doesn't leak into the child
          * if the fd table isn't shared).
          */
         if (clone_flags & CLONE_PIDFD) {
                 int flags = (clone_flags & CLONE_THREAD) ? PIDFD_THREAD : 0;
 
                 /* Note that no task has been attached to @pid yet. */
                 retval = __pidfd_prepare(pid, flags, &pidfile);
                 if (retval < 0)
                         goto bad_fork_free_pid;
                 pidfd = retval;
 
                 retval = put_user(pidfd, args->pidfd);
                 if (retval)
                         goto bad_fork_put_pidfd;
         }
 
 #ifdef CONFIG_BLOCK
         p->plug = NULL;
 #endif
         futex_init_task(p);
 
         /*
          * sigaltstack should be cleared when sharing the same VM
          */
         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
                 sas_ss_reset(p);
 
         /*
          * Syscall tracing and stepping should be turned off in the
          * child regardless of CLONE_PTRACE.
          */
         user_disable_single_step(p);
         clear_task_syscall_work(p, SYSCALL_TRACE);
 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
         clear_task_syscall_work(p, SYSCALL_EMU);
 #endif
         clear_tsk_latency_tracing(p);
 
         /* ok, now we should be set up.. */
         p->pid = pid_nr(pid);
         if (clone_flags & CLONE_THREAD) {
                 p->group_leader = current->group_leader;
                 p->tgid = current->tgid;
         } else {
                 p->group_leader = p;
                 p->tgid = p->pid;
         }
 
         p->nr_dirtied = 0;
         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
         p->dirty_paused_when = 0;
 
         p->pdeath_signal = 0;
         p->task_works = NULL;
         clear_posix_cputimers_work(p);
 
 #ifdef CONFIG_KRETPROBES
         p->kretprobe_instances.first = NULL;
 #endif
 #ifdef CONFIG_RETHOOK
         p->rethooks.first = NULL;
 #endif
 
         /*
          * Ensure that the cgroup subsystem policies allow the new process to be
          * forked. It should be noted that the new process's css_set can be changed
          * between here and cgroup_post_fork() if an organisation operation is in
          * progress.
          */
         retval = cgroup_can_fork(p, args);
         if (retval)
                 goto bad_fork_put_pidfd;
 
         /*
          * Now that the cgroups are pinned, re-clone the parent cgroup and put
          * the new task on the correct runqueue. All this *before* the task
          * becomes visible.
          *
          * This isn't part of ->can_fork() because while the re-cloning is
          * cgroup specific, it unconditionally needs to place the task on a
          * runqueue.
          */
         sched_cgroup_fork(p, args);
 
         /*
          * From this point on we must avoid any synchronous user-space
          * communication until we take the tasklist-lock. In particular, we do
          * not want user-space to be able to predict the process start-time by
          * stalling fork(2) after we recorded the start_time but before it is
          * visible to the system.
          */
 
         p->start_time = ktime_get_ns();
         p->start_boottime = ktime_get_boottime_ns();
 
         /*
          * Make it visible to the rest of the system, but dont wake it up yet.
          * Need tasklist lock for parent etc handling!
          */
         write_lock_irq(&tasklist_lock);
 
         /* CLONE_PARENT re-uses the old parent */
         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
                 p->real_parent = current->real_parent;
                 p->parent_exec_id = current->parent_exec_id;
                 if (clone_flags & CLONE_THREAD)
                         p->exit_signal = -1;
                 else
                         p->exit_signal = current->group_leader->exit_signal;
         } else {
                 p->real_parent = current;
                 p->parent_exec_id = current->self_exec_id;
                 p->exit_signal = args->exit_signal;
         }
 
         klp_copy_process(p);
 
         sched_core_fork(p);
 
         spin_lock(&current->sighand->siglock);
 
         rv_task_fork(p);
 
         rseq_fork(p, clone_flags);
 
         /* Don't start children in a dying pid namespace */
         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
                 retval = -ENOMEM;
                 goto bad_fork_cancel_cgroup;
         }
 
         /* Let kill terminate clone/fork in the middle */
         if (fatal_signal_pending(current)) {
                 retval = -EINTR;
                 goto bad_fork_cancel_cgroup;
         }
 
         /* No more failure paths after this point. */
 
         /*
          * Copy seccomp details explicitly here, in case they were changed
          * before holding sighand lock.
          */
         copy_seccomp(p);
 
         init_task_pid_links(p);
         if (likely(p->pid)) {
                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
 
                 init_task_pid(p, PIDTYPE_PID, pid);
                 if (thread_group_leader(p)) {
                         init_task_pid(p, PIDTYPE_TGID, pid);
                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
                         init_task_pid(p, PIDTYPE_SID, task_session(current));
 
                         if (is_child_reaper(pid)) {
                                 ns_of_pid(pid)->child_reaper = p;
                                 p->signal->flags |= SIGNAL_UNKILLABLE;
                         }
                         p->signal->shared_pending.signal = delayed.signal;
                         p->signal->tty = tty_kref_get(current->signal->tty);
                         /*
                          * Inherit has_child_subreaper flag under the same
                          * tasklist_lock with adding child to the process tree
                          * for propagate_has_child_subreaper optimization.
                          */
                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
                                                          p->real_parent->signal->is_child_subreaper;
                         list_add_tail(&p->sibling, &p->real_parent->children);
                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
                         attach_pid(p, PIDTYPE_TGID);
                         attach_pid(p, PIDTYPE_PGID);
                         attach_pid(p, PIDTYPE_SID);
                         __this_cpu_inc(process_counts);
                 } else {
                         current->signal->nr_threads++;
                         current->signal->quick_threads++;
                         atomic_inc(&current->signal->live);
                         refcount_inc(&current->signal->sigcnt);
                         task_join_group_stop(p);
                         list_add_tail_rcu(&p->thread_node,
                                           &p->signal->thread_head);
                 }
                 attach_pid(p, PIDTYPE_PID);
                 nr_threads++;
         }
         total_forks++;
         hlist_del_init(&delayed.node);
         spin_unlock(&current->sighand->siglock);
         syscall_tracepoint_update(p);
         write_unlock_irq(&tasklist_lock);
 
         if (pidfile)
                 fd_install(pidfd, pidfile);
 
         proc_fork_connector(p);
         sched_post_fork(p);
         cgroup_post_fork(p, args);
         perf_event_fork(p);
 
         trace_task_newtask(p, clone_flags);
         uprobe_copy_process(p, clone_flags);
         user_events_fork(p, clone_flags);
 
         copy_oom_score_adj(clone_flags, p);
 
         return p;
 
 bad_fork_cancel_cgroup:
         sched_core_free(p);
         spin_unlock(&current->sighand->siglock);
         write_unlock_irq(&tasklist_lock);
         cgroup_cancel_fork(p, args);
 bad_fork_put_pidfd:
         if (clone_flags & CLONE_PIDFD) {
                 fput(pidfile);
                 put_unused_fd(pidfd);
         }
 bad_fork_free_pid:
         if (pid != &init_struct_pid)
                 free_pid(pid);
 bad_fork_cleanup_thread:
         exit_thread(p);
 bad_fork_cleanup_io:
         if (p->io_context)
                 exit_io_context(p);
 bad_fork_cleanup_namespaces:
         exit_task_namespaces(p);
 bad_fork_cleanup_mm:
         if (p->mm) {
                 mm_clear_owner(p->mm, p);
                 mmput(p->mm);
         }
 bad_fork_cleanup_signal:
         if (!(clone_flags & CLONE_THREAD))
                 free_signal_struct(p->signal);
 bad_fork_cleanup_sighand:
         __cleanup_sighand(p->sighand);
 bad_fork_cleanup_fs:
         exit_fs(p); /* blocking */
 bad_fork_cleanup_files:
         exit_files(p); /* blocking */
 bad_fork_cleanup_semundo:
         exit_sem(p);
 bad_fork_cleanup_security:
         security_task_free(p);
 bad_fork_cleanup_audit:
         audit_free(p);
 bad_fork_cleanup_perf:
         perf_event_free_task(p);
 bad_fork_cleanup_policy:
         lockdep_free_task(p);
 #ifdef CONFIG_NUMA
         mpol_put(p->mempolicy);
 #endif
 bad_fork_cleanup_delayacct:
         delayacct_tsk_free(p);
 bad_fork_cleanup_count:
         dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
         exit_creds(p);
 bad_fork_free:
         WRITE_ONCE(p->__state, TASK_DEAD);
         exit_task_stack_account(p);
         put_task_stack(p);
         delayed_free_task(p);
 fork_out:
         spin_lock_irq(&current->sighand->siglock);
         hlist_del_init(&delayed.node);
         spin_unlock_irq(&current->sighand->siglock);
         return ERR_PTR(retval);
 }
 
 static inline void init_idle_pids(struct task_struct *idle)
 {
         enum pid_type type;
 
         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
                 init_task_pid(idle, type, &init_struct_pid);
         }
 }
 
 static int idle_dummy(void *dummy)
 {
         /* This function is never called */
         return 0;
 }
 
 struct task_struct * __init fork_idle(int cpu)
 {
         struct task_struct *task;
         struct kernel_clone_args args = {
                 .flags          = CLONE_VM,
                 .fn             = &idle_dummy,
                 .fn_arg         = NULL,
                 .kthread        = 1,
                 .idle           = 1,
         };
 
         task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
         if (!IS_ERR(task)) {
                 init_idle_pids(task);
                 init_idle(task, cpu);
         }
 
         return task;
 }
 
 /*
  * This is like kernel_clone(), but shaved down and tailored to just
  * creating io_uring workers. It returns a created task, or an error pointer.
  * The returned task is inactive, and the caller must fire it up through
  * wake_up_new_task(p). All signals are blocked in the created task.
  */
 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
 {
         unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
                                 CLONE_IO;
         struct kernel_clone_args args = {
                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
                                     CLONE_UNTRACED) & ~CSIGNAL),
                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
                 .fn             = fn,
                 .fn_arg         = arg,
                 .io_thread      = 1,
                 .user_worker    = 1,
         };
 
         return copy_process(NULL, 0, node, &args);
 }
 
 /*
  *  Ok, this is the main fork-routine.
  *
  * It copies the process, and if successful kick-starts
  * it and waits for it to finish using the VM if required.
  *
  * args->exit_signal is expected to be checked for sanity by the caller.
  */
 pid_t kernel_clone(struct kernel_clone_args *args)
 {
         u64 clone_flags = args->flags;
         struct completion vfork;
         struct pid *pid;
         struct task_struct *p;
         int trace = 0;
         pid_t nr;
 
         /*
          * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
          * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
          * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
          * field in struct clone_args and it still doesn't make sense to have
          * them both point at the same memory location. Performing this check
          * here has the advantage that we don't need to have a separate helper
          * to check for legacy clone().
          */
         if ((clone_flags & CLONE_PIDFD) &&
             (clone_flags & CLONE_PARENT_SETTID) &&
             (args->pidfd == args->parent_tid))
                 return -EINVAL;
 
         /*
          * Determine whether and which event to report to ptracer.  When
          * called from kernel_thread or CLONE_UNTRACED is explicitly
          * requested, no event is reported; otherwise, report if the event
          * for the type of forking is enabled.
          */
         if (!(clone_flags & CLONE_UNTRACED)) {
                 if (clone_flags & CLONE_VFORK)
                         trace = PTRACE_EVENT_VFORK;
                 else if (args->exit_signal != SIGCHLD)
                         trace = PTRACE_EVENT_CLONE;
                 else
                         trace = PTRACE_EVENT_FORK;
 
                 if (likely(!ptrace_event_enabled(current, trace)))
                         trace = 0;
         }
 
         p = copy_process(NULL, trace, NUMA_NO_NODE, args);
         add_latent_entropy();
 
         if (IS_ERR(p))
                 return PTR_ERR(p);
 
         /*
          * Do this prior waking up the new thread - the thread pointer
          * might get invalid after that point, if the thread exits quickly.
          */
         trace_sched_process_fork(current, p);
 
         pid = get_task_pid(p, PIDTYPE_PID);
         nr = pid_vnr(pid);
 
         if (clone_flags & CLONE_PARENT_SETTID)
                 put_user(nr, args->parent_tid);
 
         if (clone_flags & CLONE_VFORK) {
                 p->vfork_done = &vfork;
                 init_completion(&vfork);
                 get_task_struct(p);
         }
 
         if (IS_ENABLED(CONFIG_LRU_GEN_WALKS_MMU) && !(clone_flags & CLONE_VM)) {
                 /* lock the task to synchronize with memcg migration */
                 task_lock(p);
                 lru_gen_add_mm(p->mm);
                 task_unlock(p);
         }
 
         wake_up_new_task(p);
 
         /* forking complete and child started to run, tell ptracer */
         if (unlikely(trace))
                 ptrace_event_pid(trace, pid);
 
         if (clone_flags & CLONE_VFORK) {
                 if (!wait_for_vfork_done(p, &vfork))
                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
         }
 
         put_pid(pid);
         return nr;
 }
 
 /*
  * Create a kernel thread.
  */
 pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
                     unsigned long flags)
 {
         struct kernel_clone_args args = {
                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
                                     CLONE_UNTRACED) & ~CSIGNAL),
                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
                 .fn             = fn,
                 .fn_arg         = arg,
                 .name           = name,
                 .kthread        = 1,
         };
 
         return kernel_clone(&args);
 }
 
 /*
  * Create a user mode thread.
  */
 pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
 {
         struct kernel_clone_args args = {
                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
                                     CLONE_UNTRACED) & ~CSIGNAL),
                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
                 .fn             = fn,
                 .fn_arg         = arg,
         };
 
         return kernel_clone(&args);
 }
 
 #ifdef __ARCH_WANT_SYS_FORK
 SYSCALL_DEFINE0(fork)
 {
 #ifdef CONFIG_MMU
         struct kernel_clone_args args = {
                 .exit_signal = SIGCHLD,
         };
 
         return kernel_clone(&args);
 #else
         /* can not support in nommu mode */
         return -EINVAL;
 #endif
 }
 #endif
 
 #ifdef __ARCH_WANT_SYS_VFORK
 SYSCALL_DEFINE0(vfork)
 {
         struct kernel_clone_args args = {
                 .flags          = CLONE_VFORK | CLONE_VM,
                 .exit_signal    = SIGCHLD,
         };
 
         return kernel_clone(&args);
 }
 #endif
 
 #ifdef __ARCH_WANT_SYS_CLONE
 #ifdef CONFIG_CLONE_BACKWARDS
 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
                  int __user *, parent_tidptr,
                  unsigned long, tls,
                  int __user *, child_tidptr)
 #elif defined(CONFIG_CLONE_BACKWARDS2)
 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
                  int __user *, parent_tidptr,
                  int __user *, child_tidptr,
                  unsigned long, tls)
 #elif defined(CONFIG_CLONE_BACKWARDS3)
 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
                 int, stack_size,
                 int __user *, parent_tidptr,
                 int __user *, child_tidptr,
                 unsigned long, tls)
 #else
 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
                  int __user *, parent_tidptr,
                  int __user *, child_tidptr,
                  unsigned long, tls)
 #endif
 {
         struct kernel_clone_args args = {
                 .flags          = (lower_32_bits(clone_flags) & ~CSIGNAL),
                 .pidfd          = parent_tidptr,
                 .child_tid      = child_tidptr,
                 .parent_tid     = parent_tidptr,
                 .exit_signal    = (lower_32_bits(clone_flags) & CSIGNAL),
                 .stack          = newsp,
                 .tls            = tls,
         };
 
         return kernel_clone(&args);
 }
 #endif
 
 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
                                               struct clone_args __user *uargs,
                                               size_t usize)
 {
         int err;
         struct clone_args args;
         pid_t *kset_tid = kargs->set_tid;
 
         BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
                      CLONE_ARGS_SIZE_VER0);
         BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
                      CLONE_ARGS_SIZE_VER1);
         BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
                      CLONE_ARGS_SIZE_VER2);
         BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
 
         if (unlikely(usize > PAGE_SIZE))
                 return -E2BIG;
         if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
                 return -EINVAL;
 
         err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
         if (err)
                 return err;
 
         if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
                 return -EINVAL;
 
         if (unlikely(!args.set_tid && args.set_tid_size > 0))
                 return -EINVAL;
 
         if (unlikely(args.set_tid && args.set_tid_size == 0))
                 return -EINVAL;
 
         /*
          * Verify that higher 32bits of exit_signal are unset and that
          * it is a valid signal
          */
         if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
                      !valid_signal(args.exit_signal)))
                 return -EINVAL;
 
         if ((args.flags & CLONE_INTO_CGROUP) &&
             (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
                 return -EINVAL;
 
         *kargs = (struct kernel_clone_args){
                 .flags          = args.flags,
                 .pidfd          = u64_to_user_ptr(args.pidfd),
                 .child_tid      = u64_to_user_ptr(args.child_tid),
                 .parent_tid     = u64_to_user_ptr(args.parent_tid),
                 .exit_signal    = args.exit_signal,
                 .stack          = args.stack,
                 .stack_size     = args.stack_size,
                 .tls            = args.tls,
                 .set_tid_size   = args.set_tid_size,
                 .cgroup         = args.cgroup,
         };
 
         if (args.set_tid &&
                 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
                         (kargs->set_tid_size * sizeof(pid_t))))
                 return -EFAULT;
 
         kargs->set_tid = kset_tid;
 
         return 0;
 }
 
 /**
  * clone3_stack_valid - check and prepare stack
  * @kargs: kernel clone args
  *
  * Verify that the stack arguments userspace gave us are sane.
  * In addition, set the stack direction for userspace since it's easy for us to
  * determine.
  */
 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
 {
         if (kargs->stack == 0) {
                 if (kargs->stack_size > 0)
                         return false;
         } else {
                 if (kargs->stack_size == 0)
                         return false;
 
                 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
                         return false;
 
 #if !defined(CONFIG_STACK_GROWSUP)
                 kargs->stack += kargs->stack_size;
 #endif
         }
 
         return true;
 }
 
 static bool clone3_args_valid(struct kernel_clone_args *kargs)
 {
         /* Verify that no unknown flags are passed along. */
         if (kargs->flags &
             ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
                 return false;
 
         /*
          * - make the CLONE_DETACHED bit reusable for clone3
          * - make the CSIGNAL bits reusable for clone3
          */
         if (kargs->flags & (CLONE_DETACHED | (CSIGNAL & (~CLONE_NEWTIME))))
                 return false;
 
         if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
             (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
                 return false;
 
         if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
             kargs->exit_signal)
                 return false;
 
         if (!clone3_stack_valid(kargs))
                 return false;
 
         return true;
 }
 
 /**
  * sys_clone3 - create a new process with specific properties
  * @uargs: argument structure
  * @size:  size of @uargs
  *
  * clone3() is the extensible successor to clone()/clone2().
  * It takes a struct as argument that is versioned by its size.
  *
  * Return: On success, a positive PID for the child process.
  *         On error, a negative errno number.
  */
 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
 {
         int err;
 
         struct kernel_clone_args kargs;
         pid_t set_tid[MAX_PID_NS_LEVEL];
 
 #ifdef __ARCH_BROKEN_SYS_CLONE3
 #warning clone3() entry point is missing, please fix
         return -ENOSYS;
 #endif
 
         kargs.set_tid = set_tid;
 
         err = copy_clone_args_from_user(&kargs, uargs, size);
         if (err)
                 return err;
 
         if (!clone3_args_valid(&kargs))
                 return -EINVAL;
 
         return kernel_clone(&kargs);
 }
 
 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
 {
         struct task_struct *leader, *parent, *child;
         int res;
 
         read_lock(&tasklist_lock);
         leader = top = top->group_leader;
 down:
         for_each_thread(leader, parent) {
                 list_for_each_entry(child, &parent->children, sibling) {
                         res = visitor(child, data);
                         if (res) {
                                 if (res < 0)
                                         goto out;
                                 leader = child;
                                 goto down;
                         }
 up:
                         ;
                 }
         }
 
         if (leader != top) {
                 child = leader;
                 parent = child->real_parent;
                 leader = parent->group_leader;
                 goto up;
         }
 out:
         read_unlock(&tasklist_lock);
 }
 
 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
 #define ARCH_MIN_MMSTRUCT_ALIGN 0
 #endif
 
 static void sighand_ctor(void *data)
 {
         struct sighand_struct *sighand = data;
 
         spin_lock_init(&sighand->siglock);
         init_waitqueue_head(&sighand->signalfd_wqh);
 }
 
 void __init mm_cache_init(void)
 {
         unsigned int mm_size;
 
         /*
          * The mm_cpumask is located at the end of mm_struct, and is
          * dynamically sized based on the maximum CPU number this system
          * can have, taking hotplug into account (nr_cpu_ids).
          */
         mm_size = sizeof(struct mm_struct) + cpumask_size() + mm_cid_size();
 
         mm_cachep = kmem_cache_create_usercopy("mm_struct",
                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
                         offsetof(struct mm_struct, saved_auxv),
                         sizeof_field(struct mm_struct, saved_auxv),
                         NULL);
 }
 
 void __init proc_caches_init(void)
 {
         sighand_cachep = kmem_cache_create("sighand_cache",
                         sizeof(struct sighand_struct), 0,
                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
                         SLAB_ACCOUNT, sighand_ctor);
         signal_cachep = kmem_cache_create("signal_cache",
                         sizeof(struct signal_struct), 0,
                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
                         NULL);
         files_cachep = kmem_cache_create("files_cache",
                         sizeof(struct files_struct), 0,
                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
                         NULL);
         fs_cachep = kmem_cache_create("fs_cache",
                         sizeof(struct fs_struct), 0,
                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
                         NULL);
 
         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
 #ifdef CONFIG_PER_VMA_LOCK
         vma_lock_cachep = KMEM_CACHE(vma_lock, SLAB_PANIC|SLAB_ACCOUNT);
 #endif
         mmap_init();
         nsproxy_cache_init();
 }
 
 /*
  * Check constraints on flags passed to the unshare system call.
  */
 static int check_unshare_flags(unsigned long unshare_flags)
 {
         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
                                 CLONE_NEWTIME))
                 return -EINVAL;
         /*
          * Not implemented, but pretend it works if there is nothing
          * to unshare.  Note that unsharing the address space or the
          * signal handlers also need to unshare the signal queues (aka
          * CLONE_THREAD).
          */
         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
                 if (!thread_group_empty(current))
                         return -EINVAL;
         }
         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
                 if (refcount_read(&current->sighand->count) > 1)
                         return -EINVAL;
         }
         if (unshare_flags & CLONE_VM) {
                 if (!current_is_single_threaded())
                         return -EINVAL;
         }
 
         return 0;
 }
 
 /*
  * Unshare the filesystem structure if it is being shared
  */
 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
 {
         struct fs_struct *fs = current->fs;
 
         if (!(unshare_flags & CLONE_FS) || !fs)
                 return 0;
 
         /* don't need lock here; in the worst case we'll do useless copy */
         if (fs->users == 1)
                 return 0;
 
         *new_fsp = copy_fs_struct(fs);
         if (!*new_fsp)
                 return -ENOMEM;
 
         return 0;
 }
 
 /*
  * Unshare file descriptor table if it is being shared
  */
 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
 {
         struct files_struct *fd = current->files;
 
         if ((unshare_flags & CLONE_FILES) &&
             (fd && atomic_read(&fd->count) > 1)) {
                 fd = dup_fd(fd, NULL);
                 if (IS_ERR(fd))
                         return PTR_ERR(fd);
                 *new_fdp = fd;
         }
 
         return 0;
 }
 
 /*
  * unshare allows a process to 'unshare' part of the process
  * context which was originally shared using clone.  copy_*
  * functions used by kernel_clone() cannot be used here directly
  * because they modify an inactive task_struct that is being
  * constructed. Here we are modifying the current, active,
  * task_struct.
  */
 int ksys_unshare(unsigned long unshare_flags)
 {
         struct fs_struct *fs, *new_fs = NULL;
         struct files_struct *new_fd = NULL;
         struct cred *new_cred = NULL;
         struct nsproxy *new_nsproxy = NULL;
         int do_sysvsem = 0;
         int err;
 
         /*
          * If unsharing a user namespace must also unshare the thread group
          * and unshare the filesystem root and working directories.
          */
         if (unshare_flags & CLONE_NEWUSER)
                 unshare_flags |= CLONE_THREAD | CLONE_FS;
         /*
          * If unsharing vm, must also unshare signal handlers.
          */
         if (unshare_flags & CLONE_VM)
                 unshare_flags |= CLONE_SIGHAND;
         /*
          * If unsharing a signal handlers, must also unshare the signal queues.
          */
         if (unshare_flags & CLONE_SIGHAND)
                 unshare_flags |= CLONE_THREAD;
         /*
          * If unsharing namespace, must also unshare filesystem information.
          */
         if (unshare_flags & CLONE_NEWNS)
                 unshare_flags |= CLONE_FS;
 
         err = check_unshare_flags(unshare_flags);
         if (err)
                 goto bad_unshare_out;
         /*
          * CLONE_NEWIPC must also detach from the undolist: after switching
          * to a new ipc namespace, the semaphore arrays from the old
          * namespace are unreachable.
          */
         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
                 do_sysvsem = 1;
         err = unshare_fs(unshare_flags, &new_fs);
         if (err)
                 goto bad_unshare_out;
         err = unshare_fd(unshare_flags, &new_fd);
         if (err)
                 goto bad_unshare_cleanup_fs;
         err = unshare_userns(unshare_flags, &new_cred);
         if (err)
                 goto bad_unshare_cleanup_fd;
         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
                                          new_cred, new_fs);
         if (err)
                 goto bad_unshare_cleanup_cred;
 
         if (new_cred) {
                 err = set_cred_ucounts(new_cred);
                 if (err)
                         goto bad_unshare_cleanup_cred;
         }
 
         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
                 if (do_sysvsem) {
                         /*
                          * CLONE_SYSVSEM is equivalent to sys_exit().
                          */
                         exit_sem(current);
                 }
                 if (unshare_flags & CLONE_NEWIPC) {
                         /* Orphan segments in old ns (see sem above). */
                         exit_shm(current);
                         shm_init_task(current);
                 }
 
                 if (new_nsproxy)
                         switch_task_namespaces(current, new_nsproxy);
 
                 task_lock(current);
 
                 if (new_fs) {
                         fs = current->fs;
                         spin_lock(&fs->lock);
                         current->fs = new_fs;
                         if (--fs->users)
                                 new_fs = NULL;
                         else
                                 new_fs = fs;
                         spin_unlock(&fs->lock);
                 }
 
                 if (new_fd)
                         swap(current->files, new_fd);
 
                 task_unlock(current);
 
                 if (new_cred) {
                         /* Install the new user namespace */
                         commit_creds(new_cred);
                         new_cred = NULL;
                 }
         }
 
         perf_event_namespaces(current);
 
 bad_unshare_cleanup_cred:
         if (new_cred)
                 put_cred(new_cred);
 bad_unshare_cleanup_fd:
         if (new_fd)
                 put_files_struct(new_fd);
 
 bad_unshare_cleanup_fs:
         if (new_fs)
                 free_fs_struct(new_fs);
 
 bad_unshare_out:
         return err;
 }
 
 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
 {
         return ksys_unshare(unshare_flags);
 }
 
 /*
  *      Helper to unshare the files of the current task.
  *      We don't want to expose copy_files internals to
  *      the exec layer of the kernel.
  */
 
 int unshare_files(void)
 {
         struct task_struct *task = current;
         struct files_struct *old, *copy = NULL;
         int error;
 
         error = unshare_fd(CLONE_FILES, &copy);
         if (error || !copy)
                 return error;
 
         old = task->files;
         task_lock(task);
         task->files = copy;
         task_unlock(task);
         put_files_struct(old);
         return 0;
 }
 
 int sysctl_max_threads(const struct ctl_table *table, int write,
                        void *buffer, size_t *lenp, loff_t *ppos)
 {
         struct ctl_table t;
         int ret;
         int threads = max_threads;
         int min = 1;
         int max = MAX_THREADS;
 
         t = *table;
         t.data = &threads;
         t.extra1 = &min;
         t.extra2 = &max;
 
         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
         if (ret || !write)
                 return ret;
 
         max_threads = threads;
 
         return 0;
 }