1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2000-2006 Silicon Graphics, Inc.
4  * Copyright (c) 2012-2013 Red Hat, Inc.
5  * All rights reserved.
6  */
7 #include "xfs.h"
8 #include "xfs_shared.h"
9 #include "xfs_fs.h"
10 #include "xfs_format.h"
11 #include "xfs_log_format.h"
12 #include "xfs_trans_resv.h"
13 #include "xfs_bit.h"
14 #include "xfs_mount.h"
15 #include "xfs_da_format.h"
16 #include "xfs_da_btree.h"
17 #include "xfs_defer.h"
18 #include "xfs_dir2.h"
19 #include "xfs_inode.h"
20 #include "xfs_ialloc.h"
21 #include "xfs_alloc.h"
22 #include "xfs_bmap.h"
23 #include "xfs_bmap_btree.h"
24 #include "xfs_bmap_util.h"
25 #include "xfs_error.h"
26 #include "xfs_quota.h"
27 #include "xfs_trans_space.h"
28 #include "xfs_trace.h"
29 #include "xfs_symlink.h"
30 #include "xfs_trans.h"
31 #include "xfs_log.h"
32 
33 /* ----- Kernel only functions below ----- */
34 int
xfs_readlink_bmap_ilocked(struct xfs_inode * ip,char * link)35 xfs_readlink_bmap_ilocked(
36 	struct xfs_inode	*ip,
37 	char			*link)
38 {
39 	struct xfs_mount	*mp = ip->i_mount;
40 	struct xfs_bmbt_irec	mval[XFS_SYMLINK_MAPS];
41 	struct xfs_buf		*bp;
42 	xfs_daddr_t		d;
43 	char			*cur_chunk;
44 	int			pathlen = ip->i_d.di_size;
45 	int			nmaps = XFS_SYMLINK_MAPS;
46 	int			byte_cnt;
47 	int			n;
48 	int			error = 0;
49 	int			fsblocks = 0;
50 	int			offset;
51 
52 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
53 
54 	fsblocks = xfs_symlink_blocks(mp, pathlen);
55 	error = xfs_bmapi_read(ip, 0, fsblocks, mval, &nmaps, 0);
56 	if (error)
57 		goto out;
58 
59 	offset = 0;
60 	for (n = 0; n < nmaps; n++) {
61 		d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
62 		byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
63 
64 		bp = xfs_buf_read(mp->m_ddev_targp, d, BTOBB(byte_cnt), 0,
65 				  &xfs_symlink_buf_ops);
66 		if (!bp)
67 			return -ENOMEM;
68 		error = bp->b_error;
69 		if (error) {
70 			xfs_buf_ioerror_alert(bp, __func__);
71 			xfs_buf_relse(bp);
72 
73 			/* bad CRC means corrupted metadata */
74 			if (error == -EFSBADCRC)
75 				error = -EFSCORRUPTED;
76 			goto out;
77 		}
78 		byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
79 		if (pathlen < byte_cnt)
80 			byte_cnt = pathlen;
81 
82 		cur_chunk = bp->b_addr;
83 		if (xfs_sb_version_hascrc(&mp->m_sb)) {
84 			if (!xfs_symlink_hdr_ok(ip->i_ino, offset,
85 							byte_cnt, bp)) {
86 				error = -EFSCORRUPTED;
87 				xfs_alert(mp,
88 "symlink header does not match required off/len/owner (0x%x/Ox%x,0x%llx)",
89 					offset, byte_cnt, ip->i_ino);
90 				xfs_buf_relse(bp);
91 				goto out;
92 
93 			}
94 
95 			cur_chunk += sizeof(struct xfs_dsymlink_hdr);
96 		}
97 
98 		memcpy(link + offset, cur_chunk, byte_cnt);
99 
100 		pathlen -= byte_cnt;
101 		offset += byte_cnt;
102 
103 		xfs_buf_relse(bp);
104 	}
105 	ASSERT(pathlen == 0);
106 
107 	link[ip->i_d.di_size] = '\0';
108 	error = 0;
109 
110  out:
111 	return error;
112 }
113 
114 int
xfs_readlink(struct xfs_inode * ip,char * link)115 xfs_readlink(
116 	struct xfs_inode *ip,
117 	char		*link)
118 {
119 	struct xfs_mount *mp = ip->i_mount;
120 	xfs_fsize_t	pathlen;
121 	int		error = 0;
122 
123 	trace_xfs_readlink(ip);
124 
125 	ASSERT(!(ip->i_df.if_flags & XFS_IFINLINE));
126 
127 	if (XFS_FORCED_SHUTDOWN(mp))
128 		return -EIO;
129 
130 	xfs_ilock(ip, XFS_ILOCK_SHARED);
131 
132 	pathlen = ip->i_d.di_size;
133 	if (!pathlen)
134 		goto out;
135 
136 	if (pathlen < 0 || pathlen > XFS_SYMLINK_MAXLEN) {
137 		xfs_alert(mp, "%s: inode (%llu) bad symlink length (%lld)",
138 			 __func__, (unsigned long long) ip->i_ino,
139 			 (long long) pathlen);
140 		ASSERT(0);
141 		error = -EFSCORRUPTED;
142 		goto out;
143 	}
144 
145 
146 	error = xfs_readlink_bmap_ilocked(ip, link);
147 
148  out:
149 	xfs_iunlock(ip, XFS_ILOCK_SHARED);
150 	return error;
151 }
152 
153 int
xfs_symlink(struct xfs_inode * dp,struct xfs_name * link_name,const char * target_path,umode_t mode,struct xfs_inode ** ipp)154 xfs_symlink(
155 	struct xfs_inode	*dp,
156 	struct xfs_name		*link_name,
157 	const char		*target_path,
158 	umode_t			mode,
159 	struct xfs_inode	**ipp)
160 {
161 	struct xfs_mount	*mp = dp->i_mount;
162 	struct xfs_trans	*tp = NULL;
163 	struct xfs_inode	*ip = NULL;
164 	int			error = 0;
165 	int			pathlen;
166 	bool                    unlock_dp_on_error = false;
167 	xfs_fileoff_t		first_fsb;
168 	xfs_filblks_t		fs_blocks;
169 	int			nmaps;
170 	struct xfs_bmbt_irec	mval[XFS_SYMLINK_MAPS];
171 	xfs_daddr_t		d;
172 	const char		*cur_chunk;
173 	int			byte_cnt;
174 	int			n;
175 	xfs_buf_t		*bp;
176 	prid_t			prid;
177 	struct xfs_dquot	*udqp = NULL;
178 	struct xfs_dquot	*gdqp = NULL;
179 	struct xfs_dquot	*pdqp = NULL;
180 	uint			resblks;
181 
182 	*ipp = NULL;
183 
184 	trace_xfs_symlink(dp, link_name);
185 
186 	if (XFS_FORCED_SHUTDOWN(mp))
187 		return -EIO;
188 
189 	/*
190 	 * Check component lengths of the target path name.
191 	 */
192 	pathlen = strlen(target_path);
193 	if (pathlen >= XFS_SYMLINK_MAXLEN)      /* total string too long */
194 		return -ENAMETOOLONG;
195 	ASSERT(pathlen > 0);
196 
197 	udqp = gdqp = NULL;
198 	prid = xfs_get_initial_prid(dp);
199 
200 	/*
201 	 * Make sure that we have allocated dquot(s) on disk.
202 	 */
203 	error = xfs_qm_vop_dqalloc(dp,
204 			xfs_kuid_to_uid(current_fsuid()),
205 			xfs_kgid_to_gid(current_fsgid()), prid,
206 			XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
207 			&udqp, &gdqp, &pdqp);
208 	if (error)
209 		return error;
210 
211 	/*
212 	 * The symlink will fit into the inode data fork?
213 	 * There can't be any attributes so we get the whole variable part.
214 	 */
215 	if (pathlen <= XFS_LITINO(mp, dp->i_d.di_version))
216 		fs_blocks = 0;
217 	else
218 		fs_blocks = xfs_symlink_blocks(mp, pathlen);
219 	resblks = XFS_SYMLINK_SPACE_RES(mp, link_name->len, fs_blocks);
220 
221 	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_symlink, resblks, 0, 0, &tp);
222 	if (error)
223 		goto out_release_inode;
224 
225 	xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
226 	unlock_dp_on_error = true;
227 
228 	/*
229 	 * Check whether the directory allows new symlinks or not.
230 	 */
231 	if (dp->i_d.di_flags & XFS_DIFLAG_NOSYMLINKS) {
232 		error = -EPERM;
233 		goto out_trans_cancel;
234 	}
235 
236 	/*
237 	 * Reserve disk quota : blocks and inode.
238 	 */
239 	error = xfs_trans_reserve_quota(tp, mp, udqp, gdqp,
240 						pdqp, resblks, 1, 0);
241 	if (error)
242 		goto out_trans_cancel;
243 
244 	/*
245 	 * Allocate an inode for the symlink.
246 	 */
247 	error = xfs_dir_ialloc(&tp, dp, S_IFLNK | (mode & ~S_IFMT), 1, 0,
248 			       prid, &ip);
249 	if (error)
250 		goto out_trans_cancel;
251 
252 	/*
253 	 * Now we join the directory inode to the transaction.  We do not do it
254 	 * earlier because xfs_dir_ialloc might commit the previous transaction
255 	 * (and release all the locks).  An error from here on will result in
256 	 * the transaction cancel unlocking dp so don't do it explicitly in the
257 	 * error path.
258 	 */
259 	xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
260 	unlock_dp_on_error = false;
261 
262 	/*
263 	 * Also attach the dquot(s) to it, if applicable.
264 	 */
265 	xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp, pdqp);
266 
267 	if (resblks)
268 		resblks -= XFS_IALLOC_SPACE_RES(mp);
269 	/*
270 	 * If the symlink will fit into the inode, write it inline.
271 	 */
272 	if (pathlen <= XFS_IFORK_DSIZE(ip)) {
273 		xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen);
274 
275 		ip->i_d.di_size = pathlen;
276 		ip->i_d.di_format = XFS_DINODE_FMT_LOCAL;
277 		xfs_trans_log_inode(tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
278 	} else {
279 		int	offset;
280 
281 		first_fsb = 0;
282 		nmaps = XFS_SYMLINK_MAPS;
283 
284 		error = xfs_bmapi_write(tp, ip, first_fsb, fs_blocks,
285 				  XFS_BMAPI_METADATA, resblks, mval, &nmaps);
286 		if (error)
287 			goto out_trans_cancel;
288 
289 		if (resblks)
290 			resblks -= fs_blocks;
291 		ip->i_d.di_size = pathlen;
292 		xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
293 
294 		cur_chunk = target_path;
295 		offset = 0;
296 		for (n = 0; n < nmaps; n++) {
297 			char	*buf;
298 
299 			d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
300 			byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
301 			bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
302 					       BTOBB(byte_cnt), 0);
303 			if (!bp) {
304 				error = -ENOMEM;
305 				goto out_trans_cancel;
306 			}
307 			bp->b_ops = &xfs_symlink_buf_ops;
308 
309 			byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
310 			byte_cnt = min(byte_cnt, pathlen);
311 
312 			buf = bp->b_addr;
313 			buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
314 						   byte_cnt, bp);
315 
316 			memcpy(buf, cur_chunk, byte_cnt);
317 
318 			cur_chunk += byte_cnt;
319 			pathlen -= byte_cnt;
320 			offset += byte_cnt;
321 
322 			xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SYMLINK_BUF);
323 			xfs_trans_log_buf(tp, bp, 0, (buf + byte_cnt - 1) -
324 							(char *)bp->b_addr);
325 		}
326 		ASSERT(pathlen == 0);
327 	}
328 
329 	/*
330 	 * Create the directory entry for the symlink.
331 	 */
332 	error = xfs_dir_createname(tp, dp, link_name, ip->i_ino, resblks);
333 	if (error)
334 		goto out_trans_cancel;
335 	xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
336 	xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
337 
338 	/*
339 	 * If this is a synchronous mount, make sure that the
340 	 * symlink transaction goes to disk before returning to
341 	 * the user.
342 	 */
343 	if (mp->m_flags & (XFS_MOUNT_WSYNC|XFS_MOUNT_DIRSYNC)) {
344 		xfs_trans_set_sync(tp);
345 	}
346 
347 	error = xfs_trans_commit(tp);
348 	if (error)
349 		goto out_release_inode;
350 
351 	xfs_qm_dqrele(udqp);
352 	xfs_qm_dqrele(gdqp);
353 	xfs_qm_dqrele(pdqp);
354 
355 	*ipp = ip;
356 	return 0;
357 
358 out_trans_cancel:
359 	xfs_trans_cancel(tp);
360 out_release_inode:
361 	/*
362 	 * Wait until after the current transaction is aborted to finish the
363 	 * setup of the inode and release the inode.  This prevents recursive
364 	 * transactions and deadlocks from xfs_inactive.
365 	 */
366 	if (ip) {
367 		xfs_finish_inode_setup(ip);
368 		xfs_irele(ip);
369 	}
370 
371 	xfs_qm_dqrele(udqp);
372 	xfs_qm_dqrele(gdqp);
373 	xfs_qm_dqrele(pdqp);
374 
375 	if (unlock_dp_on_error)
376 		xfs_iunlock(dp, XFS_ILOCK_EXCL);
377 	return error;
378 }
379 
380 /*
381  * Free a symlink that has blocks associated with it.
382  *
383  * Note: zero length symlinks are not allowed to exist. When we set the size to
384  * zero, also change it to a regular file so that it does not get written to
385  * disk as a zero length symlink. The inode is on the unlinked list already, so
386  * userspace cannot find this inode anymore, so this change is not user visible
387  * but allows us to catch corrupt zero-length symlinks in the verifiers.
388  */
389 STATIC int
xfs_inactive_symlink_rmt(struct xfs_inode * ip)390 xfs_inactive_symlink_rmt(
391 	struct xfs_inode *ip)
392 {
393 	xfs_buf_t	*bp;
394 	int		done;
395 	int		error;
396 	int		i;
397 	xfs_mount_t	*mp;
398 	xfs_bmbt_irec_t	mval[XFS_SYMLINK_MAPS];
399 	int		nmaps;
400 	int		size;
401 	xfs_trans_t	*tp;
402 
403 	mp = ip->i_mount;
404 	ASSERT(ip->i_df.if_flags & XFS_IFEXTENTS);
405 	/*
406 	 * We're freeing a symlink that has some
407 	 * blocks allocated to it.  Free the
408 	 * blocks here.  We know that we've got
409 	 * either 1 or 2 extents and that we can
410 	 * free them all in one bunmapi call.
411 	 */
412 	ASSERT(ip->i_d.di_nextents > 0 && ip->i_d.di_nextents <= 2);
413 
414 	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
415 	if (error)
416 		return error;
417 
418 	xfs_ilock(ip, XFS_ILOCK_EXCL);
419 	xfs_trans_ijoin(tp, ip, 0);
420 
421 	/*
422 	 * Lock the inode, fix the size, turn it into a regular file and join it
423 	 * to the transaction.  Hold it so in the normal path, we still have it
424 	 * locked for the second transaction.  In the error paths we need it
425 	 * held so the cancel won't rele it, see below.
426 	 */
427 	size = (int)ip->i_d.di_size;
428 	ip->i_d.di_size = 0;
429 	VFS_I(ip)->i_mode = (VFS_I(ip)->i_mode & ~S_IFMT) | S_IFREG;
430 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
431 	/*
432 	 * Find the block(s) so we can inval and unmap them.
433 	 */
434 	done = 0;
435 	nmaps = ARRAY_SIZE(mval);
436 	error = xfs_bmapi_read(ip, 0, xfs_symlink_blocks(mp, size),
437 				mval, &nmaps, 0);
438 	if (error)
439 		goto error_trans_cancel;
440 	/*
441 	 * Invalidate the block(s). No validation is done.
442 	 */
443 	for (i = 0; i < nmaps; i++) {
444 		bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
445 			XFS_FSB_TO_DADDR(mp, mval[i].br_startblock),
446 			XFS_FSB_TO_BB(mp, mval[i].br_blockcount), 0);
447 		if (!bp) {
448 			error = -ENOMEM;
449 			goto error_trans_cancel;
450 		}
451 		xfs_trans_binval(tp, bp);
452 	}
453 	/*
454 	 * Unmap the dead block(s) to the dfops.
455 	 */
456 	error = xfs_bunmapi(tp, ip, 0, size, 0, nmaps, &done);
457 	if (error)
458 		goto error_trans_cancel;
459 	ASSERT(done);
460 
461 	/*
462 	 * Commit the transaction. This first logs the EFI and the inode, then
463 	 * rolls and commits the transaction that frees the extents.
464 	 */
465 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
466 	error = xfs_trans_commit(tp);
467 	if (error) {
468 		ASSERT(XFS_FORCED_SHUTDOWN(mp));
469 		goto error_unlock;
470 	}
471 
472 	/*
473 	 * Remove the memory for extent descriptions (just bookkeeping).
474 	 */
475 	if (ip->i_df.if_bytes)
476 		xfs_idata_realloc(ip, -ip->i_df.if_bytes, XFS_DATA_FORK);
477 	ASSERT(ip->i_df.if_bytes == 0);
478 
479 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
480 	return 0;
481 
482 error_trans_cancel:
483 	xfs_trans_cancel(tp);
484 error_unlock:
485 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
486 	return error;
487 }
488 
489 /*
490  * xfs_inactive_symlink - free a symlink
491  */
492 int
xfs_inactive_symlink(struct xfs_inode * ip)493 xfs_inactive_symlink(
494 	struct xfs_inode	*ip)
495 {
496 	struct xfs_mount	*mp = ip->i_mount;
497 	int			pathlen;
498 
499 	trace_xfs_inactive_symlink(ip);
500 
501 	if (XFS_FORCED_SHUTDOWN(mp))
502 		return -EIO;
503 
504 	xfs_ilock(ip, XFS_ILOCK_EXCL);
505 	pathlen = (int)ip->i_d.di_size;
506 	ASSERT(pathlen);
507 
508 	if (pathlen <= 0 || pathlen > XFS_SYMLINK_MAXLEN) {
509 		xfs_alert(mp, "%s: inode (0x%llx) bad symlink length (%d)",
510 			 __func__, (unsigned long long)ip->i_ino, pathlen);
511 		xfs_iunlock(ip, XFS_ILOCK_EXCL);
512 		ASSERT(0);
513 		return -EFSCORRUPTED;
514 	}
515 
516 	/*
517 	 * Inline fork state gets removed by xfs_difree() so we have nothing to
518 	 * do here in that case.
519 	 */
520 	if (ip->i_df.if_flags & XFS_IFINLINE) {
521 		xfs_iunlock(ip, XFS_ILOCK_EXCL);
522 		return 0;
523 	}
524 
525 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
526 
527 	/* remove the remote symlink */
528 	return xfs_inactive_symlink_rmt(ip);
529 }
530