TOMOYO Linux Cross Reference
Linux/fs/exec.c

   // SPDX-License-Identifier: GPL-2.0-only
   /*
    *  linux/fs/exec.c
    *
    *  Copyright (C) 1991, 1992  Linus Torvalds
    */
   
   /*
    * #!-checking implemented by tytso.
   */
  /*
   * Demand-loading implemented 01.12.91 - no need to read anything but
   * the header into memory. The inode of the executable is put into
   * "current->executable", and page faults do the actual loading. Clean.
   *
   * Once more I can proudly say that linux stood up to being changed: it
   * was less than 2 hours work to get demand-loading completely implemented.
   *
   * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
   * current->executable is only used by the procfs.  This allows a dispatch
   * table to check for several different types  of binary formats.  We keep
   * trying until we recognize the file or we run out of supported binary
   * formats.
   */
  
  #include <linux/kernel_read_file.h>
  #include <linux/slab.h>
  #include <linux/file.h>
  #include <linux/fdtable.h>
  #include <linux/mm.h>
  #include <linux/stat.h>
  #include <linux/fcntl.h>
  #include <linux/swap.h>
  #include <linux/string.h>
  #include <linux/init.h>
  #include <linux/sched/mm.h>
  #include <linux/sched/coredump.h>
  #include <linux/sched/signal.h>
  #include <linux/sched/numa_balancing.h>
  #include <linux/sched/task.h>
  #include <linux/pagemap.h>
  #include <linux/perf_event.h>
  #include <linux/highmem.h>
  #include <linux/spinlock.h>
  #include <linux/key.h>
  #include <linux/personality.h>
  #include <linux/binfmts.h>
  #include <linux/utsname.h>
  #include <linux/pid_namespace.h>
  #include <linux/module.h>
  #include <linux/namei.h>
  #include <linux/mount.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/tsacct_kern.h>
  #include <linux/cn_proc.h>
  #include <linux/audit.h>
  #include <linux/kmod.h>
  #include <linux/fsnotify.h>
  #include <linux/fs_struct.h>
  #include <linux/oom.h>
  #include <linux/compat.h>
  #include <linux/vmalloc.h>
  #include <linux/io_uring.h>
  #include <linux/syscall_user_dispatch.h>
  #include <linux/coredump.h>
  #include <linux/time_namespace.h>
  #include <linux/user_events.h>
  #include <linux/rseq.h>
  #include <linux/ksm.h>
  
  #include <linux/uaccess.h>
  #include <asm/mmu_context.h>
  #include <asm/tlb.h>
  
  #include <trace/events/task.h>
  #include "internal.h"
  
  #include <trace/events/sched.h>
  
  static int bprm_creds_from_file(struct linux_binprm *bprm);
  
  int suid_dumpable = 0;
  
  static LIST_HEAD(formats);
  static DEFINE_RWLOCK(binfmt_lock);
  
  void __register_binfmt(struct linux_binfmt * fmt, int insert)
  {
          write_lock(&binfmt_lock);
          insert ? list_add(&fmt->lh, &formats) :
                   list_add_tail(&fmt->lh, &formats);
          write_unlock(&binfmt_lock);
  }
  
  EXPORT_SYMBOL(__register_binfmt);
  
  void unregister_binfmt(struct linux_binfmt * fmt)
  {
         write_lock(&binfmt_lock);
         list_del(&fmt->lh);
         write_unlock(&binfmt_lock);
 }
 
 EXPORT_SYMBOL(unregister_binfmt);
 
 static inline void put_binfmt(struct linux_binfmt * fmt)
 {
         module_put(fmt->module);
 }
 
 bool path_noexec(const struct path *path)
 {
         return (path->mnt->mnt_flags & MNT_NOEXEC) ||
                (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 }
 
 #ifdef CONFIG_USELIB
 /*
  * Note that a shared library must be both readable and executable due to
  * security reasons.
  *
  * Also note that we take the address to load from the file itself.
  */
 SYSCALL_DEFINE1(uselib, const char __user *, library)
 {
         struct linux_binfmt *fmt;
         struct file *file;
         struct filename *tmp = getname(library);
         int error = PTR_ERR(tmp);
         static const struct open_flags uselib_flags = {
                 .open_flag = O_LARGEFILE | O_RDONLY,
                 .acc_mode = MAY_READ | MAY_EXEC,
                 .intent = LOOKUP_OPEN,
                 .lookup_flags = LOOKUP_FOLLOW,
         };
 
         if (IS_ERR(tmp))
                 goto out;
 
         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
         putname(tmp);
         error = PTR_ERR(file);
         if (IS_ERR(file))
                 goto out;
 
         /*
          * may_open() has already checked for this, so it should be
          * impossible to trip now. But we need to be extra cautious
          * and check again at the very end too.
          */
         error = -EACCES;
         if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
                          path_noexec(&file->f_path)))
                 goto exit;
 
         error = -ENOEXEC;
 
         read_lock(&binfmt_lock);
         list_for_each_entry(fmt, &formats, lh) {
                 if (!fmt->load_shlib)
                         continue;
                 if (!try_module_get(fmt->module))
                         continue;
                 read_unlock(&binfmt_lock);
                 error = fmt->load_shlib(file);
                 read_lock(&binfmt_lock);
                 put_binfmt(fmt);
                 if (error != -ENOEXEC)
                         break;
         }
         read_unlock(&binfmt_lock);
 exit:
         fput(file);
 out:
         return error;
 }
 #endif /* #ifdef CONFIG_USELIB */
 
 #ifdef CONFIG_MMU
 /*
  * The nascent bprm->mm is not visible until exec_mmap() but it can
  * use a lot of memory, account these pages in current->mm temporary
  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
  * change the counter back via acct_arg_size(0).
  */
 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 {
         struct mm_struct *mm = current->mm;
         long diff = (long)(pages - bprm->vma_pages);
 
         if (!mm || !diff)
                 return;
 
         bprm->vma_pages = pages;
         add_mm_counter(mm, MM_ANONPAGES, diff);
 }
 
 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
                 int write)
 {
         struct page *page;
         struct vm_area_struct *vma = bprm->vma;
         struct mm_struct *mm = bprm->mm;
         int ret;
 
         /*
          * Avoid relying on expanding the stack down in GUP (which
          * does not work for STACK_GROWSUP anyway), and just do it
          * by hand ahead of time.
          */
         if (write && pos < vma->vm_start) {
                 mmap_write_lock(mm);
                 ret = expand_downwards(vma, pos);
                 if (unlikely(ret < 0)) {
                         mmap_write_unlock(mm);
                         return NULL;
                 }
                 mmap_write_downgrade(mm);
         } else
                 mmap_read_lock(mm);
 
         /*
          * We are doing an exec().  'current' is the process
          * doing the exec and 'mm' is the new process's mm.
          */
         ret = get_user_pages_remote(mm, pos, 1,
                         write ? FOLL_WRITE : 0,
                         &page, NULL);
         mmap_read_unlock(mm);
         if (ret <= 0)
                 return NULL;
 
         if (write)
                 acct_arg_size(bprm, vma_pages(vma));
 
         return page;
 }
 
 static void put_arg_page(struct page *page)
 {
         put_page(page);
 }
 
 static void free_arg_pages(struct linux_binprm *bprm)
 {
 }
 
 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
                 struct page *page)
 {
         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 }
 
 static int __bprm_mm_init(struct linux_binprm *bprm)
 {
         int err;
         struct vm_area_struct *vma = NULL;
         struct mm_struct *mm = bprm->mm;
 
         bprm->vma = vma = vm_area_alloc(mm);
         if (!vma)
                 return -ENOMEM;
         vma_set_anonymous(vma);
 
         if (mmap_write_lock_killable(mm)) {
                 err = -EINTR;
                 goto err_free;
         }
 
         /*
          * Need to be called with mmap write lock
          * held, to avoid race with ksmd.
          */
         err = ksm_execve(mm);
         if (err)
                 goto err_ksm;
 
         /*
          * Place the stack at the largest stack address the architecture
          * supports. Later, we'll move this to an appropriate place. We don't
          * use STACK_TOP because that can depend on attributes which aren't
          * configured yet.
          */
         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
         vma->vm_end = STACK_TOP_MAX;
         vma->vm_start = vma->vm_end - PAGE_SIZE;
         vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP);
         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 
         err = insert_vm_struct(mm, vma);
         if (err)
                 goto err;
 
         mm->stack_vm = mm->total_vm = 1;
         mmap_write_unlock(mm);
         bprm->p = vma->vm_end - sizeof(void *);
         return 0;
 err:
         ksm_exit(mm);
 err_ksm:
         mmap_write_unlock(mm);
 err_free:
         bprm->vma = NULL;
         vm_area_free(vma);
         return err;
 }
 
 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 {
         return len <= MAX_ARG_STRLEN;
 }
 
 #else
 
 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 {
 }
 
 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
                 int write)
 {
         struct page *page;
 
         page = bprm->page[pos / PAGE_SIZE];
         if (!page && write) {
                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
                 if (!page)
                         return NULL;
                 bprm->page[pos / PAGE_SIZE] = page;
         }
 
         return page;
 }
 
 static void put_arg_page(struct page *page)
 {
 }
 
 static void free_arg_page(struct linux_binprm *bprm, int i)
 {
         if (bprm->page[i]) {
                 __free_page(bprm->page[i]);
                 bprm->page[i] = NULL;
         }
 }
 
 static void free_arg_pages(struct linux_binprm *bprm)
 {
         int i;
 
         for (i = 0; i < MAX_ARG_PAGES; i++)
                 free_arg_page(bprm, i);
 }
 
 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
                 struct page *page)
 {
 }
 
 static int __bprm_mm_init(struct linux_binprm *bprm)
 {
         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
         return 0;
 }
 
 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 {
         return len <= bprm->p;
 }
 
 #endif /* CONFIG_MMU */
 
 /*
  * Create a new mm_struct and populate it with a temporary stack
  * vm_area_struct.  We don't have enough context at this point to set the stack
  * flags, permissions, and offset, so we use temporary values.  We'll update
  * them later in setup_arg_pages().
  */
 static int bprm_mm_init(struct linux_binprm *bprm)
 {
         int err;
         struct mm_struct *mm = NULL;
 
         bprm->mm = mm = mm_alloc();
         err = -ENOMEM;
         if (!mm)
                 goto err;
 
         /* Save current stack limit for all calculations made during exec. */
         task_lock(current->group_leader);
         bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
         task_unlock(current->group_leader);
 
         err = __bprm_mm_init(bprm);
         if (err)
                 goto err;
 
         return 0;
 
 err:
         if (mm) {
                 bprm->mm = NULL;
                 mmdrop(mm);
         }
 
         return err;
 }
 
 struct user_arg_ptr {
 #ifdef CONFIG_COMPAT
         bool is_compat;
 #endif
         union {
                 const char __user *const __user *native;
 #ifdef CONFIG_COMPAT
                 const compat_uptr_t __user *compat;
 #endif
         } ptr;
 };
 
 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 {
         const char __user *native;
 
 #ifdef CONFIG_COMPAT
         if (unlikely(argv.is_compat)) {
                 compat_uptr_t compat;
 
                 if (get_user(compat, argv.ptr.compat + nr))
                         return ERR_PTR(-EFAULT);
 
                 return compat_ptr(compat);
         }
 #endif
 
         if (get_user(native, argv.ptr.native + nr))
                 return ERR_PTR(-EFAULT);
 
         return native;
 }
 
 /*
  * count() counts the number of strings in array ARGV.
  */
 static int count(struct user_arg_ptr argv, int max)
 {
         int i = 0;
 
         if (argv.ptr.native != NULL) {
                 for (;;) {
                         const char __user *p = get_user_arg_ptr(argv, i);
 
                         if (!p)
                                 break;
 
                         if (IS_ERR(p))
                                 return -EFAULT;
 
                         if (i >= max)
                                 return -E2BIG;
                         ++i;
 
                         if (fatal_signal_pending(current))
                                 return -ERESTARTNOHAND;
                         cond_resched();
                 }
         }
         return i;
 }
 
 static int count_strings_kernel(const char *const *argv)
 {
         int i;
 
         if (!argv)
                 return 0;
 
         for (i = 0; argv[i]; ++i) {
                 if (i >= MAX_ARG_STRINGS)
                         return -E2BIG;
                 if (fatal_signal_pending(current))
                         return -ERESTARTNOHAND;
                 cond_resched();
         }
         return i;
 }
 
 static inline int bprm_set_stack_limit(struct linux_binprm *bprm,
                                        unsigned long limit)
 {
 #ifdef CONFIG_MMU
         /* Avoid a pathological bprm->p. */
         if (bprm->p < limit)
                 return -E2BIG;
         bprm->argmin = bprm->p - limit;
 #endif
         return 0;
 }
 static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm)
 {
 #ifdef CONFIG_MMU
         return bprm->p < bprm->argmin;
 #else
         return false;
 #endif
 }
 
 /*
  * Calculate bprm->argmin from:
  * - _STK_LIM
  * - ARG_MAX
  * - bprm->rlim_stack.rlim_cur
  * - bprm->argc
  * - bprm->envc
  * - bprm->p
  */
 static int bprm_stack_limits(struct linux_binprm *bprm)
 {
         unsigned long limit, ptr_size;
 
         /*
          * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
          * (whichever is smaller) for the argv+env strings.
          * This ensures that:
          *  - the remaining binfmt code will not run out of stack space,
          *  - the program will have a reasonable amount of stack left
          *    to work from.
          */
         limit = _STK_LIM / 4 * 3;
         limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
         /*
          * We've historically supported up to 32 pages (ARG_MAX)
          * of argument strings even with small stacks
          */
         limit = max_t(unsigned long, limit, ARG_MAX);
         /* Reject totally pathological counts. */
         if (bprm->argc < 0 || bprm->envc < 0)
                 return -E2BIG;
         /*
          * We must account for the size of all the argv and envp pointers to
          * the argv and envp strings, since they will also take up space in
          * the stack. They aren't stored until much later when we can't
          * signal to the parent that the child has run out of stack space.
          * Instead, calculate it here so it's possible to fail gracefully.
          *
          * In the case of argc = 0, make sure there is space for adding a
          * empty string (which will bump argc to 1), to ensure confused
          * userspace programs don't start processing from argv[1], thinking
          * argc can never be 0, to keep them from walking envp by accident.
          * See do_execveat_common().
          */
         if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) ||
             check_mul_overflow(ptr_size, sizeof(void *), &ptr_size))
                 return -E2BIG;
         if (limit <= ptr_size)
                 return -E2BIG;
         limit -= ptr_size;
 
         return bprm_set_stack_limit(bprm, limit);
 }
 
 /*
  * 'copy_strings()' copies argument/environment strings from the old
  * processes's memory to the new process's stack.  The call to get_user_pages()
  * ensures the destination page is created and not swapped out.
  */
 static int copy_strings(int argc, struct user_arg_ptr argv,
                         struct linux_binprm *bprm)
 {
         struct page *kmapped_page = NULL;
         char *kaddr = NULL;
         unsigned long kpos = 0;
         int ret;
 
         while (argc-- > 0) {
                 const char __user *str;
                 int len;
                 unsigned long pos;
 
                 ret = -EFAULT;
                 str = get_user_arg_ptr(argv, argc);
                 if (IS_ERR(str))
                         goto out;
 
                 len = strnlen_user(str, MAX_ARG_STRLEN);
                 if (!len)
                         goto out;
 
                 ret = -E2BIG;
                 if (!valid_arg_len(bprm, len))
                         goto out;
 
                 /* We're going to work our way backwards. */
                 pos = bprm->p;
                 str += len;
                 bprm->p -= len;
                 if (bprm_hit_stack_limit(bprm))
                         goto out;
 
                 while (len > 0) {
                         int offset, bytes_to_copy;
 
                         if (fatal_signal_pending(current)) {
                                 ret = -ERESTARTNOHAND;
                                 goto out;
                         }
                         cond_resched();
 
                         offset = pos % PAGE_SIZE;
                         if (offset == 0)
                                 offset = PAGE_SIZE;
 
                         bytes_to_copy = offset;
                         if (bytes_to_copy > len)
                                 bytes_to_copy = len;
 
                         offset -= bytes_to_copy;
                         pos -= bytes_to_copy;
                         str -= bytes_to_copy;
                         len -= bytes_to_copy;
 
                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
                                 struct page *page;
 
                                 page = get_arg_page(bprm, pos, 1);
                                 if (!page) {
                                         ret = -E2BIG;
                                         goto out;
                                 }
 
                                 if (kmapped_page) {
                                         flush_dcache_page(kmapped_page);
                                         kunmap_local(kaddr);
                                         put_arg_page(kmapped_page);
                                 }
                                 kmapped_page = page;
                                 kaddr = kmap_local_page(kmapped_page);
                                 kpos = pos & PAGE_MASK;
                                 flush_arg_page(bprm, kpos, kmapped_page);
                         }
                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
                                 ret = -EFAULT;
                                 goto out;
                         }
                 }
         }
         ret = 0;
 out:
         if (kmapped_page) {
                 flush_dcache_page(kmapped_page);
                 kunmap_local(kaddr);
                 put_arg_page(kmapped_page);
         }
         return ret;
 }
 
 /*
  * Copy and argument/environment string from the kernel to the processes stack.
  */
 int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
 {
         int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
         unsigned long pos = bprm->p;
 
         if (len == 0)
                 return -EFAULT;
         if (!valid_arg_len(bprm, len))
                 return -E2BIG;
 
         /* We're going to work our way backwards. */
         arg += len;
         bprm->p -= len;
         if (bprm_hit_stack_limit(bprm))
                 return -E2BIG;
 
         while (len > 0) {
                 unsigned int bytes_to_copy = min_t(unsigned int, len,
                                 min_not_zero(offset_in_page(pos), PAGE_SIZE));
                 struct page *page;
 
                 pos -= bytes_to_copy;
                 arg -= bytes_to_copy;
                 len -= bytes_to_copy;
 
                 page = get_arg_page(bprm, pos, 1);
                 if (!page)
                         return -E2BIG;
                 flush_arg_page(bprm, pos & PAGE_MASK, page);
                 memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
                 put_arg_page(page);
         }
 
         return 0;
 }
 EXPORT_SYMBOL(copy_string_kernel);
 
 static int copy_strings_kernel(int argc, const char *const *argv,
                                struct linux_binprm *bprm)
 {
         while (argc-- > 0) {
                 int ret = copy_string_kernel(argv[argc], bprm);
                 if (ret < 0)
                         return ret;
                 if (fatal_signal_pending(current))
                         return -ERESTARTNOHAND;
                 cond_resched();
         }
         return 0;
 }
 
 #ifdef CONFIG_MMU
 
 /*
  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
  * the binfmt code determines where the new stack should reside, we shift it to
  * its final location.  The process proceeds as follows:
  *
  * 1) Use shift to calculate the new vma endpoints.
  * 2) Extend vma to cover both the old and new ranges.  This ensures the
  *    arguments passed to subsequent functions are consistent.
  * 3) Move vma's page tables to the new range.
  * 4) Free up any cleared pgd range.
  * 5) Shrink the vma to cover only the new range.
  */
 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 {
         struct mm_struct *mm = vma->vm_mm;
         unsigned long old_start = vma->vm_start;
         unsigned long old_end = vma->vm_end;
         unsigned long length = old_end - old_start;
         unsigned long new_start = old_start - shift;
         unsigned long new_end = old_end - shift;
         VMA_ITERATOR(vmi, mm, new_start);
         struct vm_area_struct *next;
         struct mmu_gather tlb;
 
         BUG_ON(new_start > new_end);
 
         /*
          * ensure there are no vmas between where we want to go
          * and where we are
          */
         if (vma != vma_next(&vmi))
                 return -EFAULT;
 
         vma_iter_prev_range(&vmi);
         /*
          * cover the whole range: [new_start, old_end)
          */
         if (vma_expand(&vmi, vma, new_start, old_end, vma->vm_pgoff, NULL))
                 return -ENOMEM;
 
         /*
          * move the page tables downwards, on failure we rely on
          * process cleanup to remove whatever mess we made.
          */
         if (length != move_page_tables(vma, old_start,
                                        vma, new_start, length, false, true))
                 return -ENOMEM;
 
         lru_add_drain();
         tlb_gather_mmu(&tlb, mm);
         next = vma_next(&vmi);
         if (new_end > old_start) {
                 /*
                  * when the old and new regions overlap clear from new_end.
                  */
                 free_pgd_range(&tlb, new_end, old_end, new_end,
                         next ? next->vm_start : USER_PGTABLES_CEILING);
         } else {
                 /*
                  * otherwise, clean from old_start; this is done to not touch
                  * the address space in [new_end, old_start) some architectures
                  * have constraints on va-space that make this illegal (IA64) -
                  * for the others its just a little faster.
                  */
                 free_pgd_range(&tlb, old_start, old_end, new_end,
                         next ? next->vm_start : USER_PGTABLES_CEILING);
         }
         tlb_finish_mmu(&tlb);
 
         vma_prev(&vmi);
         /* Shrink the vma to just the new range */
         return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff);
 }
 
 /*
  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
  * the stack is optionally relocated, and some extra space is added.
  */
 int setup_arg_pages(struct linux_binprm *bprm,
                     unsigned long stack_top,
                     int executable_stack)
 {
         unsigned long ret;
         unsigned long stack_shift;
         struct mm_struct *mm = current->mm;
         struct vm_area_struct *vma = bprm->vma;
         struct vm_area_struct *prev = NULL;
         unsigned long vm_flags;
         unsigned long stack_base;
         unsigned long stack_size;
         unsigned long stack_expand;
         unsigned long rlim_stack;
         struct mmu_gather tlb;
         struct vma_iterator vmi;
 
 #ifdef CONFIG_STACK_GROWSUP
         /* Limit stack size */
         stack_base = bprm->rlim_stack.rlim_max;
 
         stack_base = calc_max_stack_size(stack_base);
 
         /* Add space for stack randomization. */
         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 
         /* Make sure we didn't let the argument array grow too large. */
         if (vma->vm_end - vma->vm_start > stack_base)
                 return -ENOMEM;
 
         stack_base = PAGE_ALIGN(stack_top - stack_base);
 
         stack_shift = vma->vm_start - stack_base;
         mm->arg_start = bprm->p - stack_shift;
         bprm->p = vma->vm_end - stack_shift;
 #else
         stack_top = arch_align_stack(stack_top);
         stack_top = PAGE_ALIGN(stack_top);
 
         if (unlikely(stack_top < mmap_min_addr) ||
             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
                 return -ENOMEM;
 
         stack_shift = vma->vm_end - stack_top;
 
         bprm->p -= stack_shift;
         mm->arg_start = bprm->p;
 #endif
 
         if (bprm->loader)
                 bprm->loader -= stack_shift;
         bprm->exec -= stack_shift;
 
         if (mmap_write_lock_killable(mm))
                 return -EINTR;
 
         vm_flags = VM_STACK_FLAGS;
 
         /*
          * Adjust stack execute permissions; explicitly enable for
          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
          * (arch default) otherwise.
          */
         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
                 vm_flags |= VM_EXEC;
         else if (executable_stack == EXSTACK_DISABLE_X)
                 vm_flags &= ~VM_EXEC;
         vm_flags |= mm->def_flags;
         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 
         vma_iter_init(&vmi, mm, vma->vm_start);
 
         tlb_gather_mmu(&tlb, mm);
         ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
                         vm_flags);
         tlb_finish_mmu(&tlb);
 
         if (ret)
                 goto out_unlock;
         BUG_ON(prev != vma);
 
         if (unlikely(vm_flags & VM_EXEC)) {
                 pr_warn_once("process '%pD4' started with executable stack\n",
                              bprm->file);
         }
 
         /* Move stack pages down in memory. */
         if (stack_shift) {
                 ret = shift_arg_pages(vma, stack_shift);
                 if (ret)
                         goto out_unlock;
         }
 
         /* mprotect_fixup is overkill to remove the temporary stack flags */
         vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP);
 
         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
         stack_size = vma->vm_end - vma->vm_start;
         /*
          * Align this down to a page boundary as expand_stack
          * will align it up.
          */
         rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
 
         stack_expand = min(rlim_stack, stack_size + stack_expand);
 
 #ifdef CONFIG_STACK_GROWSUP
         stack_base = vma->vm_start + stack_expand;
 #else
         stack_base = vma->vm_end - stack_expand;
 #endif
         current->mm->start_stack = bprm->p;
         ret = expand_stack_locked(vma, stack_base);
         if (ret)
                 ret = -EFAULT;
 
 out_unlock:
         mmap_write_unlock(mm);
         return ret;
 }
 EXPORT_SYMBOL(setup_arg_pages);
 
 #else
 
 /*
  * Transfer the program arguments and environment from the holding pages
  * onto the stack. The provided stack pointer is adjusted accordingly.
  */
 int transfer_args_to_stack(struct linux_binprm *bprm,
                            unsigned long *sp_location)
 {
         unsigned long index, stop, sp;
         int ret = 0;
 
         stop = bprm->p >> PAGE_SHIFT;
         sp = *sp_location;
 
         for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
                 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
                 char *src = kmap_local_page(bprm->page[index]) + offset;
                 sp -= PAGE_SIZE - offset;
                 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
                         ret = -EFAULT;
                 kunmap_local(src);
                 if (ret)
                         goto out;
         }
 
         bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE;
         *sp_location = sp;
 
 out:
         return ret;
 }
 EXPORT_SYMBOL(transfer_args_to_stack);
 
 #endif /* CONFIG_MMU */
 
 /*
  * On success, caller must call do_close_execat() on the returned
  * struct file to close it.
  */
 static struct file *do_open_execat(int fd, struct filename *name, int flags)
 {
         struct file *file;
         int err;
         struct open_flags open_exec_flags = {
                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
                 .acc_mode = MAY_EXEC,
                 .intent = LOOKUP_OPEN,
                 .lookup_flags = LOOKUP_FOLLOW,
         };
 
         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
                 return ERR_PTR(-EINVAL);
         if (flags & AT_SYMLINK_NOFOLLOW)
                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
         if (flags & AT_EMPTY_PATH)
                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 
         file = do_filp_open(fd, name, &open_exec_flags);
         if (IS_ERR(file))
                 goto out;
 
         /*
          * may_open() has already checked for this, so it should be
          * impossible to trip now. But we need to be extra cautious
          * and check again at the very end too.
          */
         err = -EACCES;
         if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
                          path_noexec(&file->f_path)))
                 goto exit;
 
 out:
         return file;
 
 exit:
         fput(file);
         return ERR_PTR(err);
 }
 
 /**
  * open_exec - Open a path name for execution
  *
  * @name: path name to open with the intent of executing it.
  *
  * Returns ERR_PTR on failure or allocated struct file on success.
  *
  * As this is a wrapper for the internal do_open_execat(). Also see
  * do_close_execat().
  */
 struct file *open_exec(const char *name)
 {
         struct filename *filename = getname_kernel(name);
         struct file *f = ERR_CAST(filename);
 
         if (!IS_ERR(filename)) {
                 f = do_open_execat(AT_FDCWD, filename, 0);
                 putname(filename);
         }
         return f;
 }
 EXPORT_SYMBOL(open_exec);
 
 #if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC)
 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 {
         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
         if (res > 0)
                 flush_icache_user_range(addr, addr + len);
         return res;
 }
 EXPORT_SYMBOL(read_code);
 #endif
 
 /*
  * Maps the mm_struct mm into the current task struct.
  * On success, this function returns with exec_update_lock
  * held for writing.
  */
 static int exec_mmap(struct mm_struct *mm)
 {
         struct task_struct *tsk;
         struct mm_struct *old_mm, *active_mm;
         int ret;
 
         /* Notify parent that we're no longer interested in the old VM */
         tsk = current;
         old_mm = current->mm;
         exec_mm_release(tsk, old_mm);
 
         ret = down_write_killable(&tsk->signal->exec_update_lock);
         if (ret)
                 return ret;
 
         if (old_mm) {
                 /*
                  * If there is a pending fatal signal perhaps a signal
                  * whose default action is to create a coredump get
                  * out and die instead of going through with the exec.
                  */
                 ret = mmap_read_lock_killable(old_mm);
                 if (ret) {
                         up_write(&tsk->signal->exec_update_lock);
                         return ret;
                 }
         }
 
         task_lock(tsk);
         membarrier_exec_mmap(mm);
 
         local_irq_disable();
         active_mm = tsk->active_mm;
         tsk->active_mm = mm;
         tsk->mm = mm;
         mm_init_cid(mm);
         /*
          * This prevents preemption while active_mm is being loaded and
          * it and mm are being updated, which could cause problems for
          * lazy tlb mm refcounting when these are updated by context
          * switches. Not all architectures can handle irqs off over
          * activate_mm yet.
          */
         if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
                 local_irq_enable();
         activate_mm(active_mm, mm);
         if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
                 local_irq_enable();
         lru_gen_add_mm(mm);
         task_unlock(tsk);
         lru_gen_use_mm(mm);
         if (old_mm) {
                 mmap_read_unlock(old_mm);
                 BUG_ON(active_mm != old_mm);
                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
                 mm_update_next_owner(old_mm);
                 mmput(old_mm);
                 return 0;
         }
         mmdrop_lazy_tlb(active_mm);
         return 0;
 }
 
 static int de_thread(struct task_struct *tsk)
 {
         struct signal_struct *sig = tsk->signal;
         struct sighand_struct *oldsighand = tsk->sighand;
         spinlock_t *lock = &oldsighand->siglock;
 
         if (thread_group_empty(tsk))
                 goto no_thread_group;
 
         /*
          * Kill all other threads in the thread group.
          */
         spin_lock_irq(lock);
         if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) {
                 /*
                  * Another group action in progress, just
                  * return so that the signal is processed.
                  */
                 spin_unlock_irq(lock);
                 return -EAGAIN;
         }
 
         sig->group_exec_task = tsk;
         sig->notify_count = zap_other_threads(tsk);
         if (!thread_group_leader(tsk))
                 sig->notify_count--;
 
         while (sig->notify_count) {
                 __set_current_state(TASK_KILLABLE);
                 spin_unlock_irq(lock);
                 schedule();
                 if (__fatal_signal_pending(tsk))
                         goto killed;
                 spin_lock_irq(lock);
         }
         spin_unlock_irq(lock);
 
         /*
          * At this point all other threads have exited, all we have to
          * do is to wait for the thread group leader to become inactive,
          * and to assume its PID:
          */
         if (!thread_group_leader(tsk)) {
                 struct task_struct *leader = tsk->group_leader;
 
                 for (;;) {
                         cgroup_threadgroup_change_begin(tsk);
                         write_lock_irq(&tasklist_lock);
                         /*
                          * Do this under tasklist_lock to ensure that
                          * exit_notify() can't miss ->group_exec_task
                          */
                         sig->notify_count = -1;
                         if (likely(leader->exit_state))
                                 break;
                         __set_current_state(TASK_KILLABLE);
                         write_unlock_irq(&tasklist_lock);
                         cgroup_threadgroup_change_end(tsk);
                         schedule();
                         if (__fatal_signal_pending(tsk))
                                 goto killed;
                 }
 
                 /*
                  * The only record we have of the real-time age of a
                  * process, regardless of execs it's done, is start_time.
                  * All the past CPU time is accumulated in signal_struct
                  * from sister threads now dead.  But in this non-leader
                  * exec, nothing survives from the original leader thread,
                  * whose birth marks the true age of this process now.
                  * When we take on its identity by switching to its PID, we
                  * also take its birthdate (always earlier than our own).
                  */
                 tsk->start_time = leader->start_time;
                 tsk->start_boottime = leader->start_boottime;
 
                 BUG_ON(!same_thread_group(leader, tsk));
                 /*
                  * An exec() starts a new thread group with the
                  * TGID of the previous thread group. Rehash the
                  * two threads with a switched PID, and release
                  * the former thread group leader:
                  */
 
                 /* Become a process group leader with the old leader's pid.
                  * The old leader becomes a thread of the this thread group.
                  */
                 exchange_tids(tsk, leader);
                 transfer_pid(leader, tsk, PIDTYPE_TGID);
                 transfer_pid(leader, tsk, PIDTYPE_PGID);
                 transfer_pid(leader, tsk, PIDTYPE_SID);
 
                 list_replace_rcu(&leader->tasks, &tsk->tasks);
                 list_replace_init(&leader->sibling, &tsk->sibling);
 
                 tsk->group_leader = tsk;
                 leader->group_leader = tsk;
 
                 tsk->exit_signal = SIGCHLD;
                 leader->exit_signal = -1;
 
                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
                 leader->exit_state = EXIT_DEAD;
                 /*
                  * We are going to release_task()->ptrace_unlink() silently,
                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
                  * the tracer won't block again waiting for this thread.
                  */
                 if (unlikely(leader->ptrace))
                         __wake_up_parent(leader, leader->parent);
                 write_unlock_irq(&tasklist_lock);
                 cgroup_threadgroup_change_end(tsk);
 
                 release_task(leader);
         }
 
         sig->group_exec_task = NULL;
         sig->notify_count = 0;
 
 no_thread_group:
         /* we have changed execution domain */
         tsk->exit_signal = SIGCHLD;
 
         BUG_ON(!thread_group_leader(tsk));
         return 0;
 
 killed:
         /* protects against exit_notify() and __exit_signal() */
         read_lock(&tasklist_lock);
         sig->group_exec_task = NULL;
         sig->notify_count = 0;
         read_unlock(&tasklist_lock);
         return -EAGAIN;
 }
 
 
 /*
  * This function makes sure the current process has its own signal table,
  * so that flush_signal_handlers can later reset the handlers without
  * disturbing other processes.  (Other processes might share the signal
  * table via the CLONE_SIGHAND option to clone().)
  */
 static int unshare_sighand(struct task_struct *me)
 {
         struct sighand_struct *oldsighand = me->sighand;
 
         if (refcount_read(&oldsighand->count) != 1) {
                 struct sighand_struct *newsighand;
                 /*
                  * This ->sighand is shared with the CLONE_SIGHAND
                  * but not CLONE_THREAD task, switch to the new one.
                  */
                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
                 if (!newsighand)
                         return -ENOMEM;
 
                 refcount_set(&newsighand->count, 1);
 
                 write_lock_irq(&tasklist_lock);
                 spin_lock(&oldsighand->siglock);
                 memcpy(newsighand->action, oldsighand->action,
                        sizeof(newsighand->action));
                 rcu_assign_pointer(me->sighand, newsighand);
                 spin_unlock(&oldsighand->siglock);
                 write_unlock_irq(&tasklist_lock);
 
                 __cleanup_sighand(oldsighand);
         }
         return 0;
 }
 
 char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
 {
         task_lock(tsk);
         /* Always NUL terminated and zero-padded */
         strscpy_pad(buf, tsk->comm, buf_size);
         task_unlock(tsk);
         return buf;
 }
 EXPORT_SYMBOL_GPL(__get_task_comm);
 
 /*
  * These functions flushes out all traces of the currently running executable
  * so that a new one can be started
  */
 
 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
 {
         task_lock(tsk);
         trace_task_rename(tsk, buf);
         strscpy_pad(tsk->comm, buf, sizeof(tsk->comm));
         task_unlock(tsk);
         perf_event_comm(tsk, exec);
 }
 
 /*
  * Calling this is the point of no return. None of the failures will be
  * seen by userspace since either the process is already taking a fatal
  * signal (via de_thread() or coredump), or will have SEGV raised
  * (after exec_mmap()) by search_binary_handler (see below).
  */
 int begin_new_exec(struct linux_binprm * bprm)
 {
         struct task_struct *me = current;
         int retval;
 
         /* Once we are committed compute the creds */
         retval = bprm_creds_from_file(bprm);
         if (retval)
                 return retval;
 
         /*
          * This tracepoint marks the point before flushing the old exec where
          * the current task is still unchanged, but errors are fatal (point of
          * no return). The later "sched_process_exec" tracepoint is called after
          * the current task has successfully switched to the new exec.
          */
         trace_sched_prepare_exec(current, bprm);
 
         /*
          * Ensure all future errors are fatal.
          */
         bprm->point_of_no_return = true;
 
         /*
          * Make this the only thread in the thread group.
          */
         retval = de_thread(me);
         if (retval)
                 goto out;
 
         /*
          * Cancel any io_uring activity across execve
          */
         io_uring_task_cancel();
 
         /* Ensure the files table is not shared. */
         retval = unshare_files();
         if (retval)
                 goto out;
 
         /*
          * Must be called _before_ exec_mmap() as bprm->mm is
          * not visible until then. Doing it here also ensures
          * we don't race against replace_mm_exe_file().
          */
         retval = set_mm_exe_file(bprm->mm, bprm->file);
         if (retval)
                 goto out;
 
         /* If the binary is not readable then enforce mm->dumpable=0 */
         would_dump(bprm, bprm->file);
         if (bprm->have_execfd)
                 would_dump(bprm, bprm->executable);
 
         /*
          * Release all of the old mmap stuff
          */
         acct_arg_size(bprm, 0);
         retval = exec_mmap(bprm->mm);
         if (retval)
                 goto out;
 
         bprm->mm = NULL;
 
         retval = exec_task_namespaces();
         if (retval)
                 goto out_unlock;
 
 #ifdef CONFIG_POSIX_TIMERS
         spin_lock_irq(&me->sighand->siglock);
         posix_cpu_timers_exit(me);
         spin_unlock_irq(&me->sighand->siglock);
         exit_itimers(me);
         flush_itimer_signals();
 #endif
 
         /*
          * Make the signal table private.
          */
         retval = unshare_sighand(me);
         if (retval)
                 goto out_unlock;
 
         me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
         flush_thread();
         me->personality &= ~bprm->per_clear;
 
         clear_syscall_work_syscall_user_dispatch(me);
 
         /*
          * We have to apply CLOEXEC before we change whether the process is
          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
          * trying to access the should-be-closed file descriptors of a process
          * undergoing exec(2).
          */
         do_close_on_exec(me->files);
 
         if (bprm->secureexec) {
                 /* Make sure parent cannot signal privileged process. */
                 me->pdeath_signal = 0;
 
                 /*
                  * For secureexec, reset the stack limit to sane default to
                  * avoid bad behavior from the prior rlimits. This has to
                  * happen before arch_pick_mmap_layout(), which examines
                  * RLIMIT_STACK, but after the point of no return to avoid
                  * needing to clean up the change on failure.
                  */
                 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
                         bprm->rlim_stack.rlim_cur = _STK_LIM;
         }
 
         me->sas_ss_sp = me->sas_ss_size = 0;
 
         /*
          * Figure out dumpability. Note that this checking only of current
          * is wrong, but userspace depends on it. This should be testing
          * bprm->secureexec instead.
          */
         if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
             !(uid_eq(current_euid(), current_uid()) &&
               gid_eq(current_egid(), current_gid())))
                 set_dumpable(current->mm, suid_dumpable);
         else
                 set_dumpable(current->mm, SUID_DUMP_USER);
 
         perf_event_exec();
         __set_task_comm(me, kbasename(bprm->filename), true);
 
         /* An exec changes our domain. We are no longer part of the thread
            group */
         WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
         flush_signal_handlers(me, 0);
 
         retval = set_cred_ucounts(bprm->cred);
         if (retval < 0)
                 goto out_unlock;
 
         /*
          * install the new credentials for this executable
          */
         security_bprm_committing_creds(bprm);
 
         commit_creds(bprm->cred);
         bprm->cred = NULL;
 
         /*
          * Disable monitoring for regular users
          * when executing setuid binaries. Must
          * wait until new credentials are committed
          * by commit_creds() above
          */
         if (get_dumpable(me->mm) != SUID_DUMP_USER)
                 perf_event_exit_task(me);
         /*
          * cred_guard_mutex must be held at least to this point to prevent
          * ptrace_attach() from altering our determination of the task's
          * credentials; any time after this it may be unlocked.
          */
         security_bprm_committed_creds(bprm);
 
         /* Pass the opened binary to the interpreter. */
         if (bprm->have_execfd) {
                 retval = get_unused_fd_flags(0);
                 if (retval < 0)
                         goto out_unlock;
                 fd_install(retval, bprm->executable);
                 bprm->executable = NULL;
                 bprm->execfd = retval;
         }
         return 0;
 
 out_unlock:
         up_write(&me->signal->exec_update_lock);
         if (!bprm->cred)
                 mutex_unlock(&me->signal->cred_guard_mutex);
 
 out:
         return retval;
 }
 EXPORT_SYMBOL(begin_new_exec);
 
 void would_dump(struct linux_binprm *bprm, struct file *file)
 {
         struct inode *inode = file_inode(file);
         struct mnt_idmap *idmap = file_mnt_idmap(file);
         if (inode_permission(idmap, inode, MAY_READ) < 0) {
                 struct user_namespace *old, *user_ns;
                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
 
                 /* Ensure mm->user_ns contains the executable */
                 user_ns = old = bprm->mm->user_ns;
                 while ((user_ns != &init_user_ns) &&
                        !privileged_wrt_inode_uidgid(user_ns, idmap, inode))
                         user_ns = user_ns->parent;
 
                 if (old != user_ns) {
                         bprm->mm->user_ns = get_user_ns(user_ns);
                         put_user_ns(old);
                 }
         }
 }
 EXPORT_SYMBOL(would_dump);
 
 void setup_new_exec(struct linux_binprm * bprm)
 {
         /* Setup things that can depend upon the personality */
         struct task_struct *me = current;
 
         arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
 
         arch_setup_new_exec();
 
         /* Set the new mm task size. We have to do that late because it may
          * depend on TIF_32BIT which is only updated in flush_thread() on
          * some architectures like powerpc
          */
         me->mm->task_size = TASK_SIZE;
         up_write(&me->signal->exec_update_lock);
         mutex_unlock(&me->signal->cred_guard_mutex);
 }
 EXPORT_SYMBOL(setup_new_exec);
 
 /* Runs immediately before start_thread() takes over. */
 void finalize_exec(struct linux_binprm *bprm)
 {
         /* Store any stack rlimit changes before starting thread. */
         task_lock(current->group_leader);
         current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
         task_unlock(current->group_leader);
 }
 EXPORT_SYMBOL(finalize_exec);
 
 /*
  * Prepare credentials and lock ->cred_guard_mutex.
  * setup_new_exec() commits the new creds and drops the lock.
  * Or, if exec fails before, free_bprm() should release ->cred
  * and unlock.
  */
 static int prepare_bprm_creds(struct linux_binprm *bprm)
 {
         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
                 return -ERESTARTNOINTR;
 
         bprm->cred = prepare_exec_creds();
         if (likely(bprm->cred))
                 return 0;
 
         mutex_unlock(&current->signal->cred_guard_mutex);
         return -ENOMEM;
 }
 
 /* Matches do_open_execat() */
 static void do_close_execat(struct file *file)
 {
         if (file)
                 fput(file);
 }
 
 static void free_bprm(struct linux_binprm *bprm)
 {
         if (bprm->mm) {
                 acct_arg_size(bprm, 0);
                 mmput(bprm->mm);
         }
         free_arg_pages(bprm);
         if (bprm->cred) {
                 mutex_unlock(&current->signal->cred_guard_mutex);
                 abort_creds(bprm->cred);
         }
         do_close_execat(bprm->file);
         if (bprm->executable)
                 fput(bprm->executable);
         /* If a binfmt changed the interp, free it. */
         if (bprm->interp != bprm->filename)
                 kfree(bprm->interp);
         kfree(bprm->fdpath);
         kfree(bprm);
 }
 
 static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags)
 {
         struct linux_binprm *bprm;
         struct file *file;
         int retval = -ENOMEM;
 
         file = do_open_execat(fd, filename, flags);
         if (IS_ERR(file))
                 return ERR_CAST(file);
 
         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
         if (!bprm) {
                 do_close_execat(file);
                 return ERR_PTR(-ENOMEM);
         }
 
         bprm->file = file;
 
         if (fd == AT_FDCWD || filename->name[0] == '/') {
                 bprm->filename = filename->name;
         } else {
                 if (filename->name[0] == '\0')
                         bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
                 else
                         bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
                                                   fd, filename->name);
                 if (!bprm->fdpath)
                         goto out_free;
 
                 /*
                  * Record that a name derived from an O_CLOEXEC fd will be
                  * inaccessible after exec.  This allows the code in exec to
                  * choose to fail when the executable is not mmaped into the
                  * interpreter and an open file descriptor is not passed to
                  * the interpreter.  This makes for a better user experience
                  * than having the interpreter start and then immediately fail
                  * when it finds the executable is inaccessible.
                  */
                 if (get_close_on_exec(fd))
                         bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
 
                 bprm->filename = bprm->fdpath;
         }
         bprm->interp = bprm->filename;
 
         retval = bprm_mm_init(bprm);
         if (!retval)
                 return bprm;
 
 out_free:
         free_bprm(bprm);
         return ERR_PTR(retval);
 }
 
 int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
 {
         /* If a binfmt changed the interp, free it first. */
         if (bprm->interp != bprm->filename)
                 kfree(bprm->interp);
         bprm->interp = kstrdup(interp, GFP_KERNEL);
         if (!bprm->interp)
                 return -ENOMEM;
         return 0;
 }
 EXPORT_SYMBOL(bprm_change_interp);
 
 /*
  * determine how safe it is to execute the proposed program
  * - the caller must hold ->cred_guard_mutex to protect against
  *   PTRACE_ATTACH or seccomp thread-sync
  */
 static void check_unsafe_exec(struct linux_binprm *bprm)
 {
         struct task_struct *p = current, *t;
         unsigned n_fs;
 
         if (p->ptrace)
                 bprm->unsafe |= LSM_UNSAFE_PTRACE;
 
         /*
          * This isn't strictly necessary, but it makes it harder for LSMs to
          * mess up.
          */
         if (task_no_new_privs(current))
                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
 
         /*
          * If another task is sharing our fs, we cannot safely
          * suid exec because the differently privileged task
          * will be able to manipulate the current directory, etc.
          * It would be nice to force an unshare instead...
          */
         n_fs = 1;
         spin_lock(&p->fs->lock);
         rcu_read_lock();
         for_other_threads(p, t) {
                 if (t->fs == p->fs)
                         n_fs++;
         }
         rcu_read_unlock();
 
         /* "users" and "in_exec" locked for copy_fs() */
         if (p->fs->users > n_fs)
                 bprm->unsafe |= LSM_UNSAFE_SHARE;
         else
                 p->fs->in_exec = 1;
         spin_unlock(&p->fs->lock);
 }
 
 static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
 {
         /* Handle suid and sgid on files */
         struct mnt_idmap *idmap;
         struct inode *inode = file_inode(file);
         unsigned int mode;
         vfsuid_t vfsuid;
         vfsgid_t vfsgid;
 
         if (!mnt_may_suid(file->f_path.mnt))
                 return;
 
         if (task_no_new_privs(current))
                 return;
 
         mode = READ_ONCE(inode->i_mode);
         if (!(mode & (S_ISUID|S_ISGID)))
                 return;
 
         idmap = file_mnt_idmap(file);
 
         /* Be careful if suid/sgid is set */
         inode_lock(inode);
 
         /* reload atomically mode/uid/gid now that lock held */
         mode = inode->i_mode;
         vfsuid = i_uid_into_vfsuid(idmap, inode);
         vfsgid = i_gid_into_vfsgid(idmap, inode);
         inode_unlock(inode);
 
         /* We ignore suid/sgid if there are no mappings for them in the ns */
         if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
             !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))
                 return;
 
         if (mode & S_ISUID) {
                 bprm->per_clear |= PER_CLEAR_ON_SETID;
                 bprm->cred->euid = vfsuid_into_kuid(vfsuid);
         }
 
         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
                 bprm->per_clear |= PER_CLEAR_ON_SETID;
                 bprm->cred->egid = vfsgid_into_kgid(vfsgid);
         }
 }
 
 /*
  * Compute brpm->cred based upon the final binary.
  */
 static int bprm_creds_from_file(struct linux_binprm *bprm)
 {
         /* Compute creds based on which file? */
         struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
 
         bprm_fill_uid(bprm, file);
         return security_bprm_creds_from_file(bprm, file);
 }
 
 /*
  * Fill the binprm structure from the inode.
  * Read the first BINPRM_BUF_SIZE bytes
  *
  * This may be called multiple times for binary chains (scripts for example).
  */
 static int prepare_binprm(struct linux_binprm *bprm)
 {
         loff_t pos = 0;
 
         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
         return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
 }
 
 /*
  * Arguments are '\0' separated strings found at the location bprm->p
  * points to; chop off the first by relocating brpm->p to right after
  * the first '\0' encountered.
  */
 int remove_arg_zero(struct linux_binprm *bprm)
 {
         unsigned long offset;
         char *kaddr;
         struct page *page;
 
         if (!bprm->argc)
                 return 0;
 
         do {
                 offset = bprm->p & ~PAGE_MASK;
                 page = get_arg_page(bprm, bprm->p, 0);
                 if (!page)
                         return -EFAULT;
                 kaddr = kmap_local_page(page);
 
                 for (; offset < PAGE_SIZE && kaddr[offset];
                                 offset++, bprm->p++)
                         ;
 
                 kunmap_local(kaddr);
                 put_arg_page(page);
         } while (offset == PAGE_SIZE);
 
         bprm->p++;
         bprm->argc--;
 
         return 0;
 }
 EXPORT_SYMBOL(remove_arg_zero);
 
 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
 /*
  * cycle the list of binary formats handler, until one recognizes the image
  */
 static int search_binary_handler(struct linux_binprm *bprm)
 {
         bool need_retry = IS_ENABLED(CONFIG_MODULES);
         struct linux_binfmt *fmt;
         int retval;
 
         retval = prepare_binprm(bprm);
         if (retval < 0)
                 return retval;
 
         retval = security_bprm_check(bprm);
         if (retval)
                 return retval;
 
         retval = -ENOENT;
  retry:
         read_lock(&binfmt_lock);
         list_for_each_entry(fmt, &formats, lh) {
                 if (!try_module_get(fmt->module))
                         continue;
                 read_unlock(&binfmt_lock);
 
                 retval = fmt->load_binary(bprm);
 
                 read_lock(&binfmt_lock);
                 put_binfmt(fmt);
                 if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
                         read_unlock(&binfmt_lock);
                         return retval;
                 }
         }
         read_unlock(&binfmt_lock);
 
         if (need_retry) {
                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
                         return retval;
                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
                         return retval;
                 need_retry = false;
                 goto retry;
         }
 
         return retval;
 }
 
 /* binfmt handlers will call back into begin_new_exec() on success. */
 static int exec_binprm(struct linux_binprm *bprm)
 {
         pid_t old_pid, old_vpid;
         int ret, depth;
 
         /* Need to fetch pid before load_binary changes it */
         old_pid = current->pid;
         rcu_read_lock();
         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
         rcu_read_unlock();
 
         /* This allows 4 levels of binfmt rewrites before failing hard. */
         for (depth = 0;; depth++) {
                 struct file *exec;
                 if (depth > 5)
                         return -ELOOP;
 
                 ret = search_binary_handler(bprm);
                 if (ret < 0)
                         return ret;
                 if (!bprm->interpreter)
                         break;
 
                 exec = bprm->file;
                 bprm->file = bprm->interpreter;
                 bprm->interpreter = NULL;
 
                 if (unlikely(bprm->have_execfd)) {
                         if (bprm->executable) {
                                 fput(exec);
                                 return -ENOEXEC;
                         }
                         bprm->executable = exec;
                 } else
                         fput(exec);
         }
 
         audit_bprm(bprm);
         trace_sched_process_exec(current, old_pid, bprm);
         ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
         proc_exec_connector(current);
         return 0;
 }
 
 static int bprm_execve(struct linux_binprm *bprm)
 {
         int retval;
 
         retval = prepare_bprm_creds(bprm);
         if (retval)
                 return retval;
 
         /*
          * Check for unsafe execution states before exec_binprm(), which
          * will call back into begin_new_exec(), into bprm_creds_from_file(),
          * where setuid-ness is evaluated.
          */
         check_unsafe_exec(bprm);
         current->in_execve = 1;
         sched_mm_cid_before_execve(current);
 
         sched_exec();
 
         /* Set the unchanging part of bprm->cred */
         retval = security_bprm_creds_for_exec(bprm);
         if (retval)
                 goto out;
 
         retval = ccs_exec_binprm(bprm);
         if (retval < 0)
                 goto out;
 
         sched_mm_cid_after_execve(current);
         /* execve succeeded */
         current->fs->in_exec = 0;
         current->in_execve = 0;
         rseq_execve(current);
         user_events_execve(current);
         acct_update_integrals(current);
         task_numa_free(current, false);
         return retval;
 
 out:
         /*
          * If past the point of no return ensure the code never
          * returns to the userspace process.  Use an existing fatal
          * signal if present otherwise terminate the process with
          * SIGSEGV.
          */
         if (bprm->point_of_no_return && !fatal_signal_pending(current))
                 force_fatal_sig(SIGSEGV);
 
         sched_mm_cid_after_execve(current);
         current->fs->in_exec = 0;
         current->in_execve = 0;
 
         return retval;
 }
 
 static int do_execveat_common(int fd, struct filename *filename,
                               struct user_arg_ptr argv,
                               struct user_arg_ptr envp,
                               int flags)
 {
         struct linux_binprm *bprm;
         int retval;
 
         if (IS_ERR(filename))
                 return PTR_ERR(filename);
 
         /*
          * We move the actual failure in case of RLIMIT_NPROC excess from
          * set*uid() to execve() because too many poorly written programs
          * don't check setuid() return code.  Here we additionally recheck
          * whether NPROC limit is still exceeded.
          */
         if ((current->flags & PF_NPROC_EXCEEDED) &&
             is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
                 retval = -EAGAIN;
                 goto out_ret;
         }
 
         /* We're below the limit (still or again), so we don't want to make
          * further execve() calls fail. */
         current->flags &= ~PF_NPROC_EXCEEDED;
 
         bprm = alloc_bprm(fd, filename, flags);
         if (IS_ERR(bprm)) {
                 retval = PTR_ERR(bprm);
                 goto out_ret;
         }
 
         retval = count(argv, MAX_ARG_STRINGS);
         if (retval == 0)
                 pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
                              current->comm, bprm->filename);
         if (retval < 0)
                 goto out_free;
         bprm->argc = retval;
 
         retval = count(envp, MAX_ARG_STRINGS);
         if (retval < 0)
                 goto out_free;
         bprm->envc = retval;
 
         retval = bprm_stack_limits(bprm);
         if (retval < 0)
                 goto out_free;
 
         retval = copy_string_kernel(bprm->filename, bprm);
         if (retval < 0)
                 goto out_free;
         bprm->exec = bprm->p;
 
         retval = copy_strings(bprm->envc, envp, bprm);
         if (retval < 0)
                 goto out_free;
 
         retval = copy_strings(bprm->argc, argv, bprm);
         if (retval < 0)
                 goto out_free;
 
         /*
          * When argv is empty, add an empty string ("") as argv[0] to
          * ensure confused userspace programs that start processing
          * from argv[1] won't end up walking envp. See also
          * bprm_stack_limits().
          */
         if (bprm->argc == 0) {
                 retval = copy_string_kernel("", bprm);
                 if (retval < 0)
                         goto out_free;
                 bprm->argc = 1;
         }
 
         retval = bprm_execve(bprm);
 out_free:
         free_bprm(bprm);
 
 out_ret:
         putname(filename);
         return retval;
 }
 
 int kernel_execve(const char *kernel_filename,
                   const char *const *argv, const char *const *envp)
 {
         struct filename *filename;
         struct linux_binprm *bprm;
         int fd = AT_FDCWD;
         int retval;
 
         /* It is non-sense for kernel threads to call execve */
         if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
                 return -EINVAL;
 
         filename = getname_kernel(kernel_filename);
         if (IS_ERR(filename))
                 return PTR_ERR(filename);
 
         bprm = alloc_bprm(fd, filename, 0);
         if (IS_ERR(bprm)) {
                 retval = PTR_ERR(bprm);
                 goto out_ret;
         }
 
         retval = count_strings_kernel(argv);
         if (WARN_ON_ONCE(retval == 0))
                 retval = -EINVAL;
         if (retval < 0)
                 goto out_free;
         bprm->argc = retval;
 
         retval = count_strings_kernel(envp);
         if (retval < 0)
                 goto out_free;
         bprm->envc = retval;
 
         retval = bprm_stack_limits(bprm);
         if (retval < 0)
                 goto out_free;
 
         retval = copy_string_kernel(bprm->filename, bprm);
         if (retval < 0)
                 goto out_free;
         bprm->exec = bprm->p;
 
         retval = copy_strings_kernel(bprm->envc, envp, bprm);
         if (retval < 0)
                 goto out_free;
 
         retval = copy_strings_kernel(bprm->argc, argv, bprm);
         if (retval < 0)
                 goto out_free;
 
         retval = bprm_execve(bprm);
 out_free:
         free_bprm(bprm);
 out_ret:
         putname(filename);
         return retval;
 }
 
 static int do_execve(struct filename *filename,
         const char __user *const __user *__argv,
         const char __user *const __user *__envp)
 {
         struct user_arg_ptr argv = { .ptr.native = __argv };
         struct user_arg_ptr envp = { .ptr.native = __envp };
         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
 }
 
 static int do_execveat(int fd, struct filename *filename,
                 const char __user *const __user *__argv,
                 const char __user *const __user *__envp,
                 int flags)
 {
         struct user_arg_ptr argv = { .ptr.native = __argv };
         struct user_arg_ptr envp = { .ptr.native = __envp };
 
         return do_execveat_common(fd, filename, argv, envp, flags);
 }
 
 #ifdef CONFIG_COMPAT
 static int compat_do_execve(struct filename *filename,
         const compat_uptr_t __user *__argv,
         const compat_uptr_t __user *__envp)
 {
         struct user_arg_ptr argv = {
                 .is_compat = true,
                 .ptr.compat = __argv,
         };
         struct user_arg_ptr envp = {
                 .is_compat = true,
                 .ptr.compat = __envp,
         };
         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
 }
 
 static int compat_do_execveat(int fd, struct filename *filename,
                               const compat_uptr_t __user *__argv,
                               const compat_uptr_t __user *__envp,
                               int flags)
 {
         struct user_arg_ptr argv = {
                 .is_compat = true,
                 .ptr.compat = __argv,
         };
         struct user_arg_ptr envp = {
                 .is_compat = true,
                 .ptr.compat = __envp,
         };
         return do_execveat_common(fd, filename, argv, envp, flags);
 }
 #endif
 
 void set_binfmt(struct linux_binfmt *new)
 {
         struct mm_struct *mm = current->mm;
 
         if (mm->binfmt)
                 module_put(mm->binfmt->module);
 
         mm->binfmt = new;
         if (new)
                 __module_get(new->module);
 }
 EXPORT_SYMBOL(set_binfmt);
 
 /*
  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
  */
 void set_dumpable(struct mm_struct *mm, int value)
 {
         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
                 return;
 
         set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
 }
 
 SYSCALL_DEFINE3(execve,
                 const char __user *, filename,
                 const char __user *const __user *, argv,
                 const char __user *const __user *, envp)
 {
         return do_execve(getname(filename), argv, envp);
 }
 
 SYSCALL_DEFINE5(execveat,
                 int, fd, const char __user *, filename,
                 const char __user *const __user *, argv,
                 const char __user *const __user *, envp,
                 int, flags)
 {
         return do_execveat(fd,
                            getname_uflags(filename, flags),
                            argv, envp, flags);
 }
 
 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
         const compat_uptr_t __user *, argv,
         const compat_uptr_t __user *, envp)
 {
         return compat_do_execve(getname(filename), argv, envp);
 }
 
 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
                        const char __user *, filename,
                        const compat_uptr_t __user *, argv,
                        const compat_uptr_t __user *, envp,
                        int,  flags)
 {
         return compat_do_execveat(fd,
                                   getname_uflags(filename, flags),
                                   argv, envp, flags);
 }
 #endif
 
 #ifdef CONFIG_SYSCTL
 
 static int proc_dointvec_minmax_coredump(const struct ctl_table *table, int write,
                 void *buffer, size_t *lenp, loff_t *ppos)
 {
         int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 
         if (!error)
                 validate_coredump_safety();
         return error;
 }
 
 static struct ctl_table fs_exec_sysctls[] = {
         {
                 .procname       = "suid_dumpable",
                 .data           = &suid_dumpable,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec_minmax_coredump,
                 .extra1         = SYSCTL_ZERO,
                 .extra2         = SYSCTL_TWO,
         },
 };
 
 static int __init init_fs_exec_sysctls(void)
 {
         register_sysctl_init("fs", fs_exec_sysctls);
         return 0;
 }
 
 fs_initcall(init_fs_exec_sysctls);
 #endif /* CONFIG_SYSCTL */
 
 #ifdef CONFIG_EXEC_KUNIT_TEST
 #include "tests/exec_kunit.c"
 #endif
 

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