1 #include <linux/sched.h>
2 #include <linux/slab.h>
3 #include <linux/pid_namespace.h>
4 #include "internal.h"
5
6 /*
7 * /proc/self:
8 */
proc_self_readlink(struct dentry * dentry,char __user * buffer,int buflen)9 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
10 int buflen)
11 {
12 struct pid_namespace *ns = dentry->d_sb->s_fs_info;
13 pid_t tgid = task_tgid_nr_ns(current, ns);
14 char tmp[PROC_NUMBUF];
15 if (!tgid)
16 return -ENOENT;
17 sprintf(tmp, "%d", tgid);
18 return readlink_copy(buffer, buflen, tmp);
19 }
20
proc_self_follow_link(struct dentry * dentry,void ** cookie)21 static const char *proc_self_follow_link(struct dentry *dentry, void **cookie)
22 {
23 struct pid_namespace *ns = dentry->d_sb->s_fs_info;
24 pid_t tgid = task_tgid_nr_ns(current, ns);
25 char *name;
26
27 /*
28 * Not currently supported. Once we can inherit all of struct pid,
29 * we can allow this.
30 */
31 if (current->flags & PF_KTHREAD)
32 return ERR_PTR(-EOPNOTSUPP);
33
34 if (!tgid)
35 return ERR_PTR(-ENOENT);
36 /* 11 for max length of signed int in decimal + NULL term */
37 name = kmalloc(12, GFP_KERNEL);
38 if (!name)
39 return ERR_PTR(-ENOMEM);
40 sprintf(name, "%d", tgid);
41 return *cookie = name;
42 }
43
44 static const struct inode_operations proc_self_inode_operations = {
45 .readlink = proc_self_readlink,
46 .follow_link = proc_self_follow_link,
47 .put_link = kfree_put_link,
48 };
49
50 static unsigned self_inum;
51
proc_setup_self(struct super_block * s)52 int proc_setup_self(struct super_block *s)
53 {
54 struct inode *root_inode = d_inode(s->s_root);
55 struct pid_namespace *ns = s->s_fs_info;
56 struct dentry *self;
57
58 mutex_lock(&root_inode->i_mutex);
59 self = d_alloc_name(s->s_root, "self");
60 if (self) {
61 struct inode *inode = new_inode(s);
62 if (inode) {
63 inode->i_ino = self_inum;
64 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
65 inode->i_mode = S_IFLNK | S_IRWXUGO;
66 inode->i_uid = GLOBAL_ROOT_UID;
67 inode->i_gid = GLOBAL_ROOT_GID;
68 inode->i_op = &proc_self_inode_operations;
69 d_add(self, inode);
70 } else {
71 dput(self);
72 self = ERR_PTR(-ENOMEM);
73 }
74 } else {
75 self = ERR_PTR(-ENOMEM);
76 }
77 mutex_unlock(&root_inode->i_mutex);
78 if (IS_ERR(self)) {
79 pr_err("proc_fill_super: can't allocate /proc/self\n");
80 return PTR_ERR(self);
81 }
82 ns->proc_self = self;
83 return 0;
84 }
85
proc_self_init(void)86 void __init proc_self_init(void)
87 {
88 proc_alloc_inum(&self_inum);
89 }
90