blob: 82396050f18646ac0519352321637e930c05e367 [file] [log] [blame]
John Johansencdff2642010-07-29 14:47:57 -07001/*
2 * AppArmor security module
3 *
4 * This file contains AppArmor function for pathnames
5 *
6 * Copyright (C) 1998-2008 Novell/SUSE
7 * Copyright 2009-2010 Canonical Ltd.
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License as
11 * published by the Free Software Foundation, version 2 of the
12 * License.
13 */
14
15#include <linux/magic.h>
16#include <linux/mnt_namespace.h>
17#include <linux/mount.h>
18#include <linux/namei.h>
19#include <linux/nsproxy.h>
20#include <linux/path.h>
21#include <linux/sched.h>
22#include <linux/slab.h>
23#include <linux/fs_struct.h>
24
25#include "include/apparmor.h"
26#include "include/path.h"
27#include "include/policy.h"
28
29
30/* modified from dcache.c */
31static int prepend(char **buffer, int buflen, const char *str, int namelen)
32{
33 buflen -= namelen;
34 if (buflen < 0)
35 return -ENAMETOOLONG;
36 *buffer -= namelen;
37 memcpy(*buffer, str, namelen);
38 return 0;
39}
40
41#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
42
43/**
44 * d_namespace_path - lookup a name associated with a given path
45 * @path: path to lookup (NOT NULL)
46 * @buf: buffer to store path to (NOT NULL)
47 * @buflen: length of @buf
48 * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
49 * @flags: flags controlling path lookup
50 *
51 * Handle path name lookup.
52 *
53 * Returns: %0 else error code if path lookup fails
54 * When no error the path name is returned in @name which points to
55 * to a position in @buf
56 */
57static int d_namespace_path(struct path *path, char *buf, int buflen,
58 char **name, int flags)
59{
60 struct path root, tmp;
61 char *res;
John Johansene819ff52010-08-27 18:33:26 -070062 int connected, error = 0;
John Johansencdff2642010-07-29 14:47:57 -070063
Nick Piggin44672e42010-08-18 04:37:32 +100064 /* Get the root we want to resolve too, released below */
John Johansencdff2642010-07-29 14:47:57 -070065 if (flags & PATH_CHROOT_REL) {
66 /* resolve paths relative to chroot */
Nick Piggin44672e42010-08-18 04:37:32 +100067 get_fs_root(current->fs, &root);
John Johansencdff2642010-07-29 14:47:57 -070068 } else {
69 /* resolve paths relative to namespace */
70 root.mnt = current->nsproxy->mnt_ns->root;
71 root.dentry = root.mnt->mnt_root;
John Johansencdff2642010-07-29 14:47:57 -070072 path_get(&root);
73 }
74
75 spin_lock(&dcache_lock);
John Johansene819ff52010-08-27 18:33:26 -070076 tmp = root;
77 res = __d_path(path, &tmp, buf, buflen);
John Johansencdff2642010-07-29 14:47:57 -070078 spin_unlock(&dcache_lock);
79
80 *name = res;
81 /* handle error conditions - and still allow a partial path to
82 * be returned.
83 */
84 if (IS_ERR(res)) {
85 error = PTR_ERR(res);
86 *name = buf;
87 goto out;
88 }
John Johansencdff2642010-07-29 14:47:57 -070089
John Johansene819ff52010-08-27 18:33:26 -070090 /* Handle two cases:
91 * 1. A deleted dentry && profile is not allowing mediation of deleted
92 * 2. On some filesystems, newly allocated dentries appear to the
93 * security_path hooks as a deleted dentry except without an inode
94 * allocated.
95 */
96 if (d_unlinked(path->dentry) && path->dentry->d_inode &&
97 !(flags & PATH_MEDIATE_DELETED)) {
John Johansencdff2642010-07-29 14:47:57 -070098 error = -ENOENT;
99 goto out;
John Johansencdff2642010-07-29 14:47:57 -0700100 }
101
102 /* Determine if the path is connected to the expected root */
103 connected = tmp.dentry == root.dentry && tmp.mnt == root.mnt;
104
105 /* If the path is not connected,
106 * check if it is a sysctl and handle specially else remove any
107 * leading / that __d_path may have returned.
108 * Unless
109 * specifically directed to connect the path,
110 * OR
111 * if in a chroot and doing chroot relative paths and the path
112 * resolves to the namespace root (would be connected outside
113 * of chroot) and specifically directed to connect paths to
114 * namespace root.
115 */
116 if (!connected) {
117 /* is the disconnect path a sysctl? */
118 if (tmp.dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
119 strncmp(*name, "/sys/", 5) == 0) {
120 /* TODO: convert over to using a per namespace
121 * control instead of hard coded /proc
122 */
123 error = prepend(name, *name - buf, "/proc", 5);
124 } else if (!(flags & PATH_CONNECT_PATH) &&
125 !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
126 (tmp.mnt == current->nsproxy->mnt_ns->root &&
127 tmp.dentry == tmp.mnt->mnt_root))) {
128 /* disconnected path, don't return pathname starting
129 * with '/'
130 */
131 error = -ESTALE;
132 if (*res == '/')
133 *name = res + 1;
134 }
135 }
136
137out:
138 path_put(&root);
139
140 return error;
141}
142
143/**
144 * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
145 * @path: path to get name for (NOT NULL)
146 * @flags: flags controlling path lookup
147 * @buffer: buffer to put name in (NOT NULL)
148 * @size: size of buffer
149 * @name: Returns - contains position of path name in @buffer (NOT NULL)
150 *
151 * Returns: %0 else error on failure
152 */
153static int get_name_to_buffer(struct path *path, int flags, char *buffer,
154 int size, char **name)
155{
156 int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
157 int error = d_namespace_path(path, buffer, size - adjust, name, flags);
158
159 if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
160 /*
161 * Append "/" to the pathname. The root directory is a special
162 * case; it already ends in slash.
163 */
164 strcpy(&buffer[size - 2], "/");
165
166 return error;
167}
168
169/**
170 * aa_get_name - compute the pathname of a file
171 * @path: path the file (NOT NULL)
172 * @flags: flags controlling path name generation
173 * @buffer: buffer that aa_get_name() allocated (NOT NULL)
174 * @name: Returns - the generated path name if !error (NOT NULL)
175 *
176 * @name is a pointer to the beginning of the pathname (which usually differs
177 * from the beginning of the buffer), or NULL. If there is an error @name
178 * may contain a partial or invalid name that can be used for audit purposes,
179 * but it can not be used for mediation.
180 *
181 * We need PATH_IS_DIR to indicate whether the file is a directory or not
182 * because the file may not yet exist, and so we cannot check the inode's
183 * file type.
184 *
185 * Returns: %0 else error code if could retrieve name
186 */
187int aa_get_name(struct path *path, int flags, char **buffer, const char **name)
188{
189 char *buf, *str = NULL;
190 int size = 256;
191 int error;
192
193 *name = NULL;
194 *buffer = NULL;
195 for (;;) {
196 /* freed by caller */
197 buf = kmalloc(size, GFP_KERNEL);
198 if (!buf)
199 return -ENOMEM;
200
201 error = get_name_to_buffer(path, flags, buf, size, &str);
202 if (error != -ENAMETOOLONG)
203 break;
204
205 kfree(buf);
206 size <<= 1;
207 if (size > aa_g_path_max)
208 return -ENAMETOOLONG;
209 }
210 *buffer = buf;
211 *name = str;
212
213 return error;
214}