1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/cache.h>
3 #include <linux/sched.h>
4 #include <linux/slab.h>
5 #include <linux/pid_namespace.h>
6 #include "internal.h"
7
8 /*
9 * /proc/self:
10 */
11 static const char *proc_self_get_link(struct dentry *dentry,
12 struct inode *inode,
13 struct delayed_call *done)
14 {
15 struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
16 pid_t tgid = task_tgid_nr_ns(current, ns);
17 char *name;
18
19 if (!tgid)
20 return ERR_PTR(-ENOENT);
21 /* max length of unsigned int in decimal + NULL term */
22 name = kmalloc(10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
23 if (unlikely(!name))
24 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
25 sprintf(name, "%u", tgid);
26 set_delayed_call(done, kfree_link, name);
27 return name;
28 }
29
30 static const struct inode_operations proc_self_inode_operations = {
31 .get_link = proc_self_get_link,
32 };
33
34 static unsigned self_inum __ro_after_init;
35
36 int proc_setup_self(struct super_block *s)
37 {
38 struct inode *root_inode = d_inode(s->s_root);
39 struct proc_fs_info *fs_info = proc_sb_info(s);
40 struct dentry *self;
41 int ret = -ENOMEM;
42
43 inode_lock(root_inode);
44 self = d_alloc_name(s->s_root, "self");
45 if (self) {
46 struct inode *inode = new_inode(s);
47 if (inode) {
48 inode->i_ino = self_inum;
49 simple_inode_init_ts(inode);
50 inode->i_mode = S_IFLNK | S_IRWXUGO;
51 inode->i_uid = GLOBAL_ROOT_UID;
52 inode->i_gid = GLOBAL_ROOT_GID;
53 inode->i_op = &proc_self_inode_operations;
54 d_add(self, inode);
55 ret = 0;
56 } else {
57 dput(self);
58 }
59 }
60 inode_unlock(root_inode);
61
62 if (ret)
63 pr_err("proc_fill_super: can't allocate /proc/self\n");
64 else
65 fs_info->proc_self = self;
66
67 return ret;
68 }
69
70 void __init proc_self_init(void)
71 {
72 proc_alloc_inum(&self_inum);
73 }
74
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