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 */
11static 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->i_sb);
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
30static const struct inode_operations proc_self_inode_operations = {
31	.get_link	= proc_self_get_link,
 
 
32};
33
34static unsigned self_inum __ro_after_init;
35
36int proc_setup_self(struct super_block *s)
37{
38	struct inode *root_inode = d_inode(s->s_root);
39	struct proc_fs_info *fs_info = proc_sb_info(s);
40	struct dentry *self;
41	int ret = -ENOMEM;
42
43	inode_lock(root_inode);
44	self = d_alloc_name(s->s_root, "self");
45	if (self) {
46		struct inode *inode = new_inode(s);
47		if (inode) {
48			inode->i_ino = self_inum;
49			simple_inode_init_ts(inode);
50			inode->i_mode = S_IFLNK | S_IRWXUGO;
51			inode->i_uid = GLOBAL_ROOT_UID;
52			inode->i_gid = GLOBAL_ROOT_GID;
53			inode->i_op = &proc_self_inode_operations;
54			d_add(self, inode);
55			ret = 0;
56		} else {
57			dput(self);
 
58		}
 
 
59	}
60	inode_unlock(root_inode);
61
62	if (ret)
63		pr_err("proc_fill_super: can't allocate /proc/self\n");
64	else
65		fs_info->proc_self = self;
66
67	return ret;
68}
69
70void __init proc_self_init(void)
71{
72	proc_alloc_inum(&self_inum);
73}

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