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Miklos Szeredie9be9d52014-10-24 00:14:38 +02001/*
2 *
3 * Copyright (C) 2011 Novell Inc.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
8 */
9
10#include <linux/fs.h>
11#include <linux/slab.h>
12#include <linux/xattr.h>
Miklos Szeredi5201dc42016-09-01 11:11:59 +020013#include <linux/posix_acl.h>
Miklos Szeredie9be9d52014-10-24 00:14:38 +020014#include "overlayfs.h"
15
Al Viro0f7ff2d2015-12-06 12:31:07 -050016static int ovl_copy_up_truncate(struct dentry *dentry)
Miklos Szeredie9be9d52014-10-24 00:14:38 +020017{
18 int err;
19 struct dentry *parent;
20 struct kstat stat;
21 struct path lowerpath;
Vivek Goyal8eac98b2016-09-06 13:40:32 -040022 const struct cred *old_cred;
Miklos Szeredie9be9d52014-10-24 00:14:38 +020023
24 parent = dget_parent(dentry);
25 err = ovl_copy_up(parent);
26 if (err)
27 goto out_dput_parent;
28
29 ovl_path_lower(dentry, &lowerpath);
Miklos Szeredie9be9d52014-10-24 00:14:38 +020030
Vivek Goyal8eac98b2016-09-06 13:40:32 -040031 old_cred = ovl_override_creds(dentry->d_sb);
32 err = vfs_getattr(&lowerpath, &stat);
33 if (!err) {
34 stat.size = 0;
35 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
36 }
37 revert_creds(old_cred);
Miklos Szeredie9be9d52014-10-24 00:14:38 +020038
39out_dput_parent:
40 dput(parent);
41 return err;
42}
43
44int ovl_setattr(struct dentry *dentry, struct iattr *attr)
45{
46 int err;
47 struct dentry *upperdentry;
Vivek Goyal1175b6b2016-07-01 16:34:28 -040048 const struct cred *old_cred;
Miklos Szeredie9be9d52014-10-24 00:14:38 +020049
Miklos Szeredicf9a6782015-12-11 16:30:49 +010050 /*
51 * Check for permissions before trying to copy-up. This is redundant
52 * since it will be rechecked later by ->setattr() on upper dentry. But
53 * without this, copy-up can be triggered by just about anybody.
54 *
55 * We don't initialize inode->size, which just means that
56 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
57 * check for a swapfile (which this won't be anyway).
58 */
Jan Kara31051c82016-05-26 16:55:18 +020059 err = setattr_prepare(dentry, attr);
Miklos Szeredicf9a6782015-12-11 16:30:49 +010060 if (err)
61 return err;
62
Miklos Szeredie9be9d52014-10-24 00:14:38 +020063 err = ovl_want_write(dentry);
64 if (err)
65 goto out;
66
Miklos Szeredi03bea602016-06-29 16:03:55 +020067 if (attr->ia_valid & ATTR_SIZE) {
68 struct inode *realinode = d_inode(ovl_dentry_real(dentry));
69
70 err = -ETXTBSY;
71 if (atomic_read(&realinode->i_writecount) < 0)
72 goto out_drop_write;
73 }
74
Miklos Szerediacff81e2015-12-04 19:18:48 +010075 err = ovl_copy_up(dentry);
76 if (!err) {
Miklos Szeredi03bea602016-06-29 16:03:55 +020077 struct inode *winode = NULL;
78
Miklos Szerediacff81e2015-12-04 19:18:48 +010079 upperdentry = ovl_dentry_upper(dentry);
80
Miklos Szeredi03bea602016-06-29 16:03:55 +020081 if (attr->ia_valid & ATTR_SIZE) {
82 winode = d_inode(upperdentry);
83 err = get_write_access(winode);
84 if (err)
85 goto out_drop_write;
86 }
87
Miklos Szeredib99c2d92016-07-04 16:49:48 +020088 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
89 attr->ia_valid &= ~ATTR_MODE;
90
Al Viro59551022016-01-22 15:40:57 -050091 inode_lock(upperdentry->d_inode);
Vivek Goyal1175b6b2016-07-01 16:34:28 -040092 old_cred = ovl_override_creds(dentry->d_sb);
Miklos Szeredie9be9d52014-10-24 00:14:38 +020093 err = notify_change(upperdentry, attr, NULL);
Vivek Goyal1175b6b2016-07-01 16:34:28 -040094 revert_creds(old_cred);
Konstantin Khlebnikovb81de062016-01-31 16:21:29 +030095 if (!err)
96 ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
Al Viro59551022016-01-22 15:40:57 -050097 inode_unlock(upperdentry->d_inode);
Miklos Szeredi03bea602016-06-29 16:03:55 +020098
99 if (winode)
100 put_write_access(winode);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200101 }
Miklos Szeredi03bea602016-06-29 16:03:55 +0200102out_drop_write:
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200103 ovl_drop_write(dentry);
104out:
105 return err;
106}
107
108static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
109 struct kstat *stat)
110{
111 struct path realpath;
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400112 const struct cred *old_cred;
113 int err;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200114
115 ovl_path_real(dentry, &realpath);
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400116 old_cred = ovl_override_creds(dentry->d_sb);
117 err = vfs_getattr(&realpath, stat);
118 revert_creds(old_cred);
119 return err;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200120}
121
122int ovl_permission(struct inode *inode, int mask)
123{
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200124 bool is_upper;
Miklos Szeredi39b681f2016-07-29 12:05:24 +0200125 struct inode *realinode = ovl_inode_real(inode, &is_upper);
Vivek Goyalc0ca3d72016-07-01 16:34:27 -0400126 const struct cred *old_cred;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200127 int err;
128
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200129 /* Careful in RCU walk mode */
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200130 if (!realinode) {
131 WARN_ON(!(mask & MAY_NOT_BLOCK));
Miklos Szeredia999d7e2016-07-29 12:05:23 +0200132 return -ECHILD;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200133 }
134
Vivek Goyalc0ca3d72016-07-01 16:34:27 -0400135 /*
136 * Check overlay inode with the creds of task and underlying inode
137 * with creds of mounter
138 */
139 err = generic_permission(inode, mask);
140 if (err)
141 return err;
142
143 old_cred = ovl_override_creds(inode->i_sb);
Vivek Goyal500cac32016-07-13 11:00:14 -0400144 if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
Vivek Goyal754f8cb2016-07-01 16:34:29 -0400145 mask &= ~(MAY_WRITE | MAY_APPEND);
Vivek Goyal500cac32016-07-13 11:00:14 -0400146 /* Make sure mounter can read file for copy up later */
147 mask |= MAY_READ;
148 }
Miklos Szeredi9c630eb2016-07-29 12:05:23 +0200149 err = inode_permission(realinode, mask);
Vivek Goyalc0ca3d72016-07-01 16:34:27 -0400150 revert_creds(old_cred);
151
152 return err;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200153}
154
Al Viro6b255392015-11-17 10:20:54 -0500155static const char *ovl_get_link(struct dentry *dentry,
Al Virofceef392015-12-29 15:58:39 -0500156 struct inode *inode,
157 struct delayed_call *done)
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200158{
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400159 const struct cred *old_cred;
160 const char *p;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200161
Al Viro6b255392015-11-17 10:20:54 -0500162 if (!dentry)
163 return ERR_PTR(-ECHILD);
164
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400165 old_cred = ovl_override_creds(dentry->d_sb);
Miklos Szeredi77642352016-10-04 14:40:45 +0200166 p = vfs_get_link(ovl_dentry_real(dentry), done);
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400167 revert_creds(old_cred);
168 return p;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200169}
170
Miklos Szeredi09562542016-08-08 15:08:49 +0200171bool ovl_is_private_xattr(const char *name)
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200172{
Andreas Gruenbacherfe2b7592016-08-22 17:59:22 +0200173 return strncmp(name, OVL_XATTR_PREFIX,
174 sizeof(OVL_XATTR_PREFIX) - 1) == 0;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200175}
176
Andreas Gruenbacher0e585cc2016-08-22 17:22:11 +0200177int ovl_xattr_set(struct dentry *dentry, const char *name, const void *value,
178 size_t size, int flags)
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200179{
180 int err;
Andreas Gruenbacher0e585cc2016-08-22 17:22:11 +0200181 struct path realpath;
182 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400183 const struct cred *old_cred;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200184
185 err = ovl_want_write(dentry);
186 if (err)
187 goto out;
188
Andreas Gruenbacher0e585cc2016-08-22 17:22:11 +0200189 if (!value && !OVL_TYPE_UPPER(type)) {
190 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
191 if (err < 0)
192 goto out_drop_write;
193 }
194
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200195 err = ovl_copy_up(dentry);
196 if (err)
197 goto out_drop_write;
198
Andreas Gruenbacher0e585cc2016-08-22 17:22:11 +0200199 if (!OVL_TYPE_UPPER(type))
200 ovl_path_upper(dentry, &realpath);
201
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400202 old_cred = ovl_override_creds(dentry->d_sb);
Andreas Gruenbacher0e585cc2016-08-22 17:22:11 +0200203 if (value)
204 err = vfs_setxattr(realpath.dentry, name, value, size, flags);
205 else {
206 WARN_ON(flags != XATTR_REPLACE);
207 err = vfs_removexattr(realpath.dentry, name);
208 }
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400209 revert_creds(old_cred);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200210
211out_drop_write:
212 ovl_drop_write(dentry);
213out:
214 return err;
215}
216
Andreas Gruenbacher0eb45fc2016-08-22 17:52:55 +0200217int ovl_xattr_get(struct dentry *dentry, const char *name,
218 void *value, size_t size)
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200219{
Miklos Szeredib5817552016-06-06 16:21:37 +0200220 struct dentry *realdentry = ovl_dentry_real(dentry);
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400221 ssize_t res;
222 const struct cred *old_cred;
Miklos Szeredi52148462014-11-20 16:40:00 +0100223
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400224 old_cred = ovl_override_creds(dentry->d_sb);
225 res = vfs_getxattr(realdentry, name, value, size);
226 revert_creds(old_cred);
227 return res;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200228}
229
Miklos Szeredib2a40ea2017-05-29 15:15:27 +0200230static bool ovl_can_list(const char *s)
231{
232 /* List all non-trusted xatts */
233 if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
234 return true;
235
236 /* Never list trusted.overlay, list other trusted for superuser only */
Mark Salyzyn3fe1e272019-08-29 11:30:14 -0700237 return !ovl_is_private_xattr(s) &&
238 ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
Miklos Szeredib2a40ea2017-05-29 15:15:27 +0200239}
240
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200241ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
242{
Miklos Szeredib5817552016-06-06 16:21:37 +0200243 struct dentry *realdentry = ovl_dentry_real(dentry);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200244 ssize_t res;
Miklos Szeredi7cb35112016-09-01 11:12:00 +0200245 size_t len;
246 char *s;
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400247 const struct cred *old_cred;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200248
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400249 old_cred = ovl_override_creds(dentry->d_sb);
Miklos Szeredib5817552016-06-06 16:21:37 +0200250 res = vfs_listxattr(realdentry, list, size);
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400251 revert_creds(old_cred);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200252 if (res <= 0 || size == 0)
253 return res;
254
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200255 /* filter out private xattrs */
Miklos Szeredi7cb35112016-09-01 11:12:00 +0200256 for (s = list, len = res; len;) {
257 size_t slen = strnlen(s, len) + 1;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200258
Miklos Szeredi7cb35112016-09-01 11:12:00 +0200259 /* underlying fs providing us with an broken xattr list? */
260 if (WARN_ON(slen > len))
261 return -EIO;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200262
Miklos Szeredi7cb35112016-09-01 11:12:00 +0200263 len -= slen;
Miklos Szeredib2a40ea2017-05-29 15:15:27 +0200264 if (!ovl_can_list(s)) {
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200265 res -= slen;
Miklos Szeredi7cb35112016-09-01 11:12:00 +0200266 memmove(s, s + slen, len);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200267 } else {
Miklos Szeredi7cb35112016-09-01 11:12:00 +0200268 s += slen;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200269 }
270 }
271
272 return res;
273}
274
Vivek Goyal39a25b22016-07-01 16:34:26 -0400275struct posix_acl *ovl_get_acl(struct inode *inode, int type)
276{
Miklos Szeredi39b681f2016-07-29 12:05:24 +0200277 struct inode *realinode = ovl_inode_real(inode, NULL);
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400278 const struct cred *old_cred;
279 struct posix_acl *acl;
Vivek Goyal39a25b22016-07-01 16:34:26 -0400280
Miklos Szeredi5201dc42016-09-01 11:11:59 +0200281 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
Vivek Goyal39a25b22016-07-01 16:34:26 -0400282 return NULL;
283
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400284 old_cred = ovl_override_creds(inode->i_sb);
Miklos Szeredi5201dc42016-09-01 11:11:59 +0200285 acl = get_acl(realinode, type);
Vivek Goyal1175b6b2016-07-01 16:34:28 -0400286 revert_creds(old_cred);
287
288 return acl;
Vivek Goyal39a25b22016-07-01 16:34:26 -0400289}
290
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200291static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
292 struct dentry *realdentry)
293{
Miklos Szeredi1afaba12014-12-13 00:59:42 +0100294 if (OVL_TYPE_UPPER(type))
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200295 return false;
296
297 if (special_file(realdentry->d_inode->i_mode))
298 return false;
299
300 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
301 return false;
302
303 return true;
304}
305
Miklos Szeredi2d902672016-06-30 08:53:27 +0200306int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200307{
Miklos Szeredi2d902672016-06-30 08:53:27 +0200308 int err = 0;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200309 struct path realpath;
310 enum ovl_path_type type;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200311
312 type = ovl_path_real(dentry, &realpath);
David Howells4bacc9c2015-06-18 14:32:31 +0100313 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200314 err = ovl_want_write(dentry);
Miklos Szeredi2d902672016-06-30 08:53:27 +0200315 if (!err) {
316 if (file_flags & O_TRUNC)
317 err = ovl_copy_up_truncate(dentry);
318 else
319 err = ovl_copy_up(dentry);
320 ovl_drop_write(dentry);
321 }
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200322 }
323
Miklos Szeredi2d902672016-06-30 08:53:27 +0200324 return err;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200325}
326
Miklos Szeredid719e8f2016-07-29 12:05:23 +0200327int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
328{
329 struct dentry *alias;
330 struct path upperpath;
331
332 if (!(flags & S_ATIME))
333 return 0;
334
335 alias = d_find_any_alias(inode);
336 if (!alias)
337 return 0;
338
339 ovl_path_upper(alias, &upperpath);
340 if (upperpath.dentry) {
341 touch_atime(&upperpath);
342 inode->i_atime = d_inode(upperpath.dentry)->i_atime;
343 }
344
345 dput(alias);
346
347 return 0;
348}
349
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200350static const struct inode_operations ovl_file_inode_operations = {
351 .setattr = ovl_setattr,
352 .permission = ovl_permission,
353 .getattr = ovl_getattr,
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200354 .listxattr = ovl_listxattr,
Vivek Goyal39a25b22016-07-01 16:34:26 -0400355 .get_acl = ovl_get_acl,
Miklos Szeredid719e8f2016-07-29 12:05:23 +0200356 .update_time = ovl_update_time,
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200357};
358
359static const struct inode_operations ovl_symlink_inode_operations = {
360 .setattr = ovl_setattr,
Al Viro6b255392015-11-17 10:20:54 -0500361 .get_link = ovl_get_link,
Miklos Szeredi78a3fa42016-10-04 14:40:44 +0200362 .readlink = generic_readlink,
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200363 .getattr = ovl_getattr,
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200364 .listxattr = ovl_listxattr,
Miklos Szeredid719e8f2016-07-29 12:05:23 +0200365 .update_time = ovl_update_time,
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200366};
367
Miklos Szeredi51f7e522016-07-29 12:05:24 +0200368static void ovl_fill_inode(struct inode *inode, umode_t mode)
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200369{
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200370 inode->i_ino = get_next_ino();
371 inode->i_mode = mode;
Miklos Szeredid719e8f2016-07-29 12:05:23 +0200372 inode->i_flags |= S_NOCMTIME;
Miklos Szeredi2a3a2a32016-09-01 11:11:59 +0200373#ifdef CONFIG_FS_POSIX_ACL
374 inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
375#endif
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200376
Vivek Goyal07a2daa2016-07-01 16:34:25 -0400377 mode &= S_IFMT;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200378 switch (mode) {
379 case S_IFDIR:
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200380 inode->i_op = &ovl_dir_inode_operations;
381 inode->i_fop = &ovl_dir_operations;
382 break;
383
384 case S_IFLNK:
385 inode->i_op = &ovl_symlink_inode_operations;
386 break;
387
Miklos Szeredi51f7e522016-07-29 12:05:24 +0200388 default:
389 WARN(1, "illegal file type: %i\n", mode);
390 /* Fall through */
391
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200392 case S_IFREG:
393 case S_IFSOCK:
394 case S_IFBLK:
395 case S_IFCHR:
396 case S_IFIFO:
397 inode->i_op = &ovl_file_inode_operations;
398 break;
Miklos Szeredi51f7e522016-07-29 12:05:24 +0200399 }
400}
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200401
Miklos Szeredi51f7e522016-07-29 12:05:24 +0200402struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)
403{
404 struct inode *inode;
405
406 inode = new_inode(sb);
407 if (inode)
408 ovl_fill_inode(inode, mode);
409
410 return inode;
411}
412
413static int ovl_inode_test(struct inode *inode, void *data)
414{
415 return ovl_inode_real(inode, NULL) == data;
416}
417
418static int ovl_inode_set(struct inode *inode, void *data)
419{
420 inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
421 return 0;
422}
423
424struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
425
426{
427 struct inode *inode;
428
429 inode = iget5_locked(sb, (unsigned long) realinode,
430 ovl_inode_test, ovl_inode_set, realinode);
431 if (inode && inode->i_state & I_NEW) {
432 ovl_fill_inode(inode, realinode->i_mode);
433 set_nlink(inode, realinode->i_nlink);
434 unlock_new_inode(inode);
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200435 }
436
437 return inode;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200438}