GNU Linux-libre 4.19.211-gnu1
[releases.git] / fs / proc / 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/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);
16         pid_t tgid = task_tgid_nr_ns(current, ns);
17         char *name;
18
19         /*
20          * Not currently supported. Once we can inherit all of struct pid,
21          * we can allow this.
22          */
23         if (current->flags & PF_KTHREAD)
24                 return ERR_PTR(-EOPNOTSUPP);
25
26         if (!tgid)
27                 return ERR_PTR(-ENOENT);
28         /* max length of unsigned int in decimal + NULL term */
29         name = kmalloc(10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
30         if (unlikely(!name))
31                 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
32         sprintf(name, "%u", tgid);
33         set_delayed_call(done, kfree_link, name);
34         return name;
35 }
36
37 static const struct inode_operations proc_self_inode_operations = {
38         .get_link       = proc_self_get_link,
39 };
40
41 static unsigned self_inum __ro_after_init;
42
43 int proc_setup_self(struct super_block *s)
44 {
45         struct inode *root_inode = d_inode(s->s_root);
46         struct pid_namespace *ns = proc_pid_ns(root_inode);
47         struct dentry *self;
48         
49         inode_lock(root_inode);
50         self = d_alloc_name(s->s_root, "self");
51         if (self) {
52                 struct inode *inode = new_inode(s);
53                 if (inode) {
54                         inode->i_ino = self_inum;
55                         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
56                         inode->i_mode = S_IFLNK | S_IRWXUGO;
57                         inode->i_uid = GLOBAL_ROOT_UID;
58                         inode->i_gid = GLOBAL_ROOT_GID;
59                         inode->i_op = &proc_self_inode_operations;
60                         d_add(self, inode);
61                 } else {
62                         dput(self);
63                         self = ERR_PTR(-ENOMEM);
64                 }
65         } else {
66                 self = ERR_PTR(-ENOMEM);
67         }
68         inode_unlock(root_inode);
69         if (IS_ERR(self)) {
70                 pr_err("proc_fill_super: can't allocate /proc/self\n");
71                 return PTR_ERR(self);
72         }
73         ns->proc_self = self;
74         return 0;
75 }
76
77 void __init proc_self_init(void)
78 {
79         proc_alloc_inum(&self_inum);
80 }