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 /*
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
proc_setup_self(struct super_block * s)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
proc_self_init(void)77 void __init proc_self_init(void)
78 {
79 proc_alloc_inum(&self_inum);
80 }
81