1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 2017 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
5 */
6 #include "xfs.h"
7 #include "xfs_fs.h"
8 #include "xfs_shared.h"
9 #include "xfs_format.h"
10 #include "xfs_trans_resv.h"
11 #include "xfs_mount.h"
12 #include "xfs_defer.h"
13 #include "xfs_btree.h"
14 #include "xfs_bit.h"
15 #include "xfs_log_format.h"
16 #include "xfs_trans.h"
17 #include "xfs_sb.h"
18 #include "xfs_inode.h"
19 #include "xfs_icache.h"
20 #include "xfs_dir2.h"
21 #include "xfs_dir2_priv.h"
22 #include "xfs_ialloc.h"
23 #include "scrub/xfs_scrub.h"
24 #include "scrub/scrub.h"
25 #include "scrub/common.h"
26 #include "scrub/trace.h"
27
28 /* Set us up to scrub parents. */
29 int
xchk_setup_parent(struct xfs_scrub * sc,struct xfs_inode * ip)30 xchk_setup_parent(
31 struct xfs_scrub *sc,
32 struct xfs_inode *ip)
33 {
34 return xchk_setup_inode_contents(sc, ip, 0);
35 }
36
37 /* Parent pointers */
38
39 /* Look for an entry in a parent pointing to this inode. */
40
41 struct xchk_parent_ctx {
42 struct dir_context dc;
43 xfs_ino_t ino;
44 xfs_nlink_t nlink;
45 };
46
47 /* Look for a single entry in a directory pointing to an inode. */
48 STATIC int
xchk_parent_actor(struct dir_context * dc,const char * name,int namelen,loff_t pos,u64 ino,unsigned type)49 xchk_parent_actor(
50 struct dir_context *dc,
51 const char *name,
52 int namelen,
53 loff_t pos,
54 u64 ino,
55 unsigned type)
56 {
57 struct xchk_parent_ctx *spc;
58
59 spc = container_of(dc, struct xchk_parent_ctx, dc);
60 if (spc->ino == ino)
61 spc->nlink++;
62 return 0;
63 }
64
65 /* Count the number of dentries in the parent dir that point to this inode. */
66 STATIC int
xchk_parent_count_parent_dentries(struct xfs_scrub * sc,struct xfs_inode * parent,xfs_nlink_t * nlink)67 xchk_parent_count_parent_dentries(
68 struct xfs_scrub *sc,
69 struct xfs_inode *parent,
70 xfs_nlink_t *nlink)
71 {
72 struct xchk_parent_ctx spc = {
73 .dc.actor = xchk_parent_actor,
74 .dc.pos = 0,
75 .ino = sc->ip->i_ino,
76 .nlink = 0,
77 };
78 size_t bufsize;
79 loff_t oldpos;
80 uint lock_mode;
81 int error = 0;
82
83 /*
84 * If there are any blocks, read-ahead block 0 as we're almost
85 * certain to have the next operation be a read there. This is
86 * how we guarantee that the parent's extent map has been loaded,
87 * if there is one.
88 */
89 lock_mode = xfs_ilock_data_map_shared(parent);
90 if (parent->i_d.di_nextents > 0)
91 error = xfs_dir3_data_readahead(parent, 0, -1);
92 xfs_iunlock(parent, lock_mode);
93 if (error)
94 return error;
95
96 /*
97 * Iterate the parent dir to confirm that there is
98 * exactly one entry pointing back to the inode being
99 * scanned.
100 */
101 bufsize = (size_t)min_t(loff_t, XFS_READDIR_BUFSIZE,
102 parent->i_d.di_size);
103 oldpos = 0;
104 while (true) {
105 error = xfs_readdir(sc->tp, parent, &spc.dc, bufsize);
106 if (error)
107 goto out;
108 if (oldpos == spc.dc.pos)
109 break;
110 oldpos = spc.dc.pos;
111 }
112 *nlink = spc.nlink;
113 out:
114 return error;
115 }
116
117 /*
118 * Given the inode number of the alleged parent of the inode being
119 * scrubbed, try to validate that the parent has exactly one directory
120 * entry pointing back to the inode being scrubbed.
121 */
122 STATIC int
xchk_parent_validate(struct xfs_scrub * sc,xfs_ino_t dnum,bool * try_again)123 xchk_parent_validate(
124 struct xfs_scrub *sc,
125 xfs_ino_t dnum,
126 bool *try_again)
127 {
128 struct xfs_mount *mp = sc->mp;
129 struct xfs_inode *dp = NULL;
130 xfs_nlink_t expected_nlink;
131 xfs_nlink_t nlink;
132 int error = 0;
133
134 *try_again = false;
135
136 if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
137 goto out;
138
139 /* '..' must not point to ourselves. */
140 if (sc->ip->i_ino == dnum) {
141 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
142 goto out;
143 }
144
145 /*
146 * If we're an unlinked directory, the parent /won't/ have a link
147 * to us. Otherwise, it should have one link.
148 */
149 expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1;
150
151 /*
152 * Grab this parent inode. We release the inode before we
153 * cancel the scrub transaction. Since we're don't know a
154 * priori that releasing the inode won't trigger eofblocks
155 * cleanup (which allocates what would be a nested transaction)
156 * if the parent pointer erroneously points to a file, we
157 * can't use DONTCACHE here because DONTCACHE inodes can trigger
158 * immediate inactive cleanup of the inode.
159 *
160 * If _iget returns -EINVAL then the parent inode number is garbage
161 * and the directory is corrupt. If the _iget returns -EFSCORRUPTED
162 * or -EFSBADCRC then the parent is corrupt which is a cross
163 * referencing error. Any other error is an operational error.
164 */
165 error = xfs_iget(mp, sc->tp, dnum, XFS_IGET_UNTRUSTED, 0, &dp);
166 if (error == -EINVAL) {
167 error = -EFSCORRUPTED;
168 xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error);
169 goto out;
170 }
171 if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
172 goto out;
173 if (dp == sc->ip || !S_ISDIR(VFS_I(dp)->i_mode)) {
174 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
175 goto out_rele;
176 }
177
178 /*
179 * We prefer to keep the inode locked while we lock and search
180 * its alleged parent for a forward reference. If we can grab
181 * the iolock, validate the pointers and we're done. We must
182 * use nowait here to avoid an ABBA deadlock on the parent and
183 * the child inodes.
184 */
185 if (xfs_ilock_nowait(dp, XFS_IOLOCK_SHARED)) {
186 error = xchk_parent_count_parent_dentries(sc, dp, &nlink);
187 if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0,
188 &error))
189 goto out_unlock;
190 if (nlink != expected_nlink)
191 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
192 goto out_unlock;
193 }
194
195 /*
196 * The game changes if we get here. We failed to lock the parent,
197 * so we're going to try to verify both pointers while only holding
198 * one lock so as to avoid deadlocking with something that's actually
199 * trying to traverse down the directory tree.
200 */
201 xfs_iunlock(sc->ip, sc->ilock_flags);
202 sc->ilock_flags = 0;
203 error = xchk_ilock_inverted(dp, XFS_IOLOCK_SHARED);
204 if (error)
205 goto out_rele;
206
207 /* Go looking for our dentry. */
208 error = xchk_parent_count_parent_dentries(sc, dp, &nlink);
209 if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
210 goto out_unlock;
211
212 /* Drop the parent lock, relock this inode. */
213 xfs_iunlock(dp, XFS_IOLOCK_SHARED);
214 error = xchk_ilock_inverted(sc->ip, XFS_IOLOCK_EXCL);
215 if (error)
216 goto out_rele;
217 sc->ilock_flags = XFS_IOLOCK_EXCL;
218
219 /*
220 * If we're an unlinked directory, the parent /won't/ have a link
221 * to us. Otherwise, it should have one link. We have to re-set
222 * it here because we dropped the lock on sc->ip.
223 */
224 expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1;
225
226 /* Look up '..' to see if the inode changed. */
227 error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL);
228 if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
229 goto out_rele;
230
231 /* Drat, parent changed. Try again! */
232 if (dnum != dp->i_ino) {
233 xfs_irele(dp);
234 *try_again = true;
235 return 0;
236 }
237 xfs_irele(dp);
238
239 /*
240 * '..' didn't change, so check that there was only one entry
241 * for us in the parent.
242 */
243 if (nlink != expected_nlink)
244 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
245 return error;
246
247 out_unlock:
248 xfs_iunlock(dp, XFS_IOLOCK_SHARED);
249 out_rele:
250 xfs_irele(dp);
251 out:
252 return error;
253 }
254
255 /* Scrub a parent pointer. */
256 int
xchk_parent(struct xfs_scrub * sc)257 xchk_parent(
258 struct xfs_scrub *sc)
259 {
260 struct xfs_mount *mp = sc->mp;
261 xfs_ino_t dnum;
262 bool try_again;
263 int tries = 0;
264 int error = 0;
265
266 /*
267 * If we're a directory, check that the '..' link points up to
268 * a directory that has one entry pointing to us.
269 */
270 if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
271 return -ENOENT;
272
273 /* We're not a special inode, are we? */
274 if (!xfs_verify_dir_ino(mp, sc->ip->i_ino)) {
275 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
276 goto out;
277 }
278
279 /*
280 * The VFS grabs a read or write lock via i_rwsem before it reads
281 * or writes to a directory. If we've gotten this far we've
282 * already obtained IOLOCK_EXCL, which (since 4.10) is the same as
283 * getting a write lock on i_rwsem. Therefore, it is safe for us
284 * to drop the ILOCK here in order to do directory lookups.
285 */
286 sc->ilock_flags &= ~(XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL);
287 xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL);
288
289 /* Look up '..' */
290 error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL);
291 if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
292 goto out;
293 if (!xfs_verify_dir_ino(mp, dnum)) {
294 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
295 goto out;
296 }
297
298 /* Is this the root dir? Then '..' must point to itself. */
299 if (sc->ip == mp->m_rootip) {
300 if (sc->ip->i_ino != mp->m_sb.sb_rootino ||
301 sc->ip->i_ino != dnum)
302 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
303 goto out;
304 }
305
306 do {
307 error = xchk_parent_validate(sc, dnum, &try_again);
308 if (error)
309 goto out;
310 } while (try_again && ++tries < 20);
311
312 /*
313 * We gave it our best shot but failed, so mark this scrub
314 * incomplete. Userspace can decide if it wants to try again.
315 */
316 if (try_again && tries == 20)
317 xchk_set_incomplete(sc);
318 out:
319 /*
320 * If we failed to lock the parent inode even after a retry, just mark
321 * this scrub incomplete and return.
322 */
323 if (sc->try_harder && error == -EDEADLOCK) {
324 error = 0;
325 xchk_set_incomplete(sc);
326 }
327 return error;
328 }
329