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 */
proc_self_get_link(struct dentry * dentry,struct inode * inode,struct delayed_call * done)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 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
proc_setup_self(struct super_block * s)36 int proc_setup_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 *self;
41
42 inode_lock(root_inode);
43 self = d_alloc_name(s->s_root, "self");
44 if (self) {
45 struct inode *inode = new_inode_pseudo(s);
46 if (inode) {
47 inode->i_ino = 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_self_inode_operations;
53 d_add(self, inode);
54 } else {
55 dput(self);
56 self = ERR_PTR(-ENOMEM);
57 }
58 } else {
59 self = ERR_PTR(-ENOMEM);
60 }
61 inode_unlock(root_inode);
62 if (IS_ERR(self)) {
63 pr_err("proc_fill_super: can't allocate /proc/self\n");
64 return PTR_ERR(self);
65 }
66 ns->proc_self = self;
67 return 0;
68 }
69
proc_self_init(void)70 void __init proc_self_init(void)
71 {
72 proc_alloc_inum(&self_inum);
73 }
74
