GNU Linux-libre 4.19.211-gnu1
[releases.git] / fs / proc / thread_self.c
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/thread_self:
10  */
11 static const char *proc_thread_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);
16         pid_t tgid = task_tgid_nr_ns(current, ns);
17         pid_t pid = task_pid_nr_ns(current, ns);
18         char *name;
19
20         if (!pid)
21                 return ERR_PTR(-ENOENT);
22         name = kmalloc(10 + 6 + 10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
23         if (unlikely(!name))
24                 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
25         sprintf(name, "%u/task/%u", tgid, pid);
26         set_delayed_call(done, kfree_link, name);
27         return name;
28 }
29
30 static const struct inode_operations proc_thread_self_inode_operations = {
31         .get_link       = proc_thread_self_get_link,
32 };
33
34 static unsigned thread_self_inum __ro_after_init;
35
36 int proc_setup_thread_self(struct super_block *s)
37 {
38         struct inode *root_inode = d_inode(s->s_root);
39         struct pid_namespace *ns = proc_pid_ns(root_inode);
40         struct dentry *thread_self;
41
42         inode_lock(root_inode);
43         thread_self = d_alloc_name(s->s_root, "thread-self");
44         if (thread_self) {
45                 struct inode *inode = new_inode(s);
46                 if (inode) {
47                         inode->i_ino = thread_self_inum;
48                         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
49                         inode->i_mode = S_IFLNK | S_IRWXUGO;
50                         inode->i_uid = GLOBAL_ROOT_UID;
51                         inode->i_gid = GLOBAL_ROOT_GID;
52                         inode->i_op = &proc_thread_self_inode_operations;
53                         d_add(thread_self, inode);
54                 } else {
55                         dput(thread_self);
56                         thread_self = ERR_PTR(-ENOMEM);
57                 }
58         } else {
59                 thread_self = ERR_PTR(-ENOMEM);
60         }
61         inode_unlock(root_inode);
62         if (IS_ERR(thread_self)) {
63                 pr_err("proc_fill_super: can't allocate /proc/thread_self\n");
64                 return PTR_ERR(thread_self);
65         }
66         ns->proc_thread_self = thread_self;
67         return 0;
68 }
69
70 void __init proc_thread_self_init(void)
71 {
72         proc_alloc_inum(&thread_self_inum);
73 }