summaryrefslogtreecommitdiff
path: root/fs/cifs/dfs.c
blob: b64d20374b9c853d4402ef3f8617dbfa57921d94 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2022 Paulo Alcantara <palcantara@suse.de>
 */

#include <linux/namei.h>
#include "cifsproto.h"
#include "cifs_debug.h"
#include "dns_resolve.h"
#include "fs_context.h"
#include "dfs.h"

/**
 * dfs_parse_target_referral - set fs context for dfs target referral
 *
 * @full_path: full path in UNC format.
 * @ref: dfs referral pointer.
 * @ctx: smb3 fs context pointer.
 *
 * Return zero if dfs referral was parsed correctly, otherwise non-zero.
 */
int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
			      struct smb3_fs_context *ctx)
{
	int rc;
	const char *prepath = NULL;
	char *path;

	if (!full_path || !*full_path || !ref || !ctx)
		return -EINVAL;

	if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
		return -EINVAL;

	if (strlen(full_path) - ref->path_consumed) {
		prepath = full_path + ref->path_consumed;
		/* skip initial delimiter */
		if (*prepath == '/' || *prepath == '\\')
			prepath++;
	}

	path = cifs_build_devname(ref->node_name, prepath);
	if (IS_ERR(path))
		return PTR_ERR(path);

	rc = smb3_parse_devname(path, ctx);
	if (rc)
		goto out;

	rc = dns_resolve_server_name_to_ip(path, (struct sockaddr *)&ctx->dstaddr, NULL);

out:
	kfree(path);
	return rc;
}

/*
 * cifs_build_path_to_root returns full path to root when we do not have an
 * existing connection (tcon)
 */
static char *build_unc_path_to_root(const struct smb3_fs_context *ctx,
				    const struct cifs_sb_info *cifs_sb, bool useppath)
{
	char *full_path, *pos;
	unsigned int pplen = useppath && ctx->prepath ? strlen(ctx->prepath) + 1 : 0;
	unsigned int unc_len = strnlen(ctx->UNC, MAX_TREE_SIZE + 1);

	if (unc_len > MAX_TREE_SIZE)
		return ERR_PTR(-EINVAL);

	full_path = kmalloc(unc_len + pplen + 1, GFP_KERNEL);
	if (full_path == NULL)
		return ERR_PTR(-ENOMEM);

	memcpy(full_path, ctx->UNC, unc_len);
	pos = full_path + unc_len;

	if (pplen) {
		*pos = CIFS_DIR_SEP(cifs_sb);
		memcpy(pos + 1, ctx->prepath, pplen);
		pos += pplen;
	}

	*pos = '\0'; /* add trailing null */
	convert_delimiter(full_path, CIFS_DIR_SEP(cifs_sb));
	cifs_dbg(FYI, "%s: full_path=%s\n", __func__, full_path);
	return full_path;
}

static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
{
	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
	int rc;

	ctx->leaf_fullpath = (char *)full_path;
	rc = cifs_mount_get_session(mnt_ctx);
	ctx->leaf_fullpath = NULL;
	if (!rc) {
		struct cifs_ses *ses = mnt_ctx->ses;

		mutex_lock(&ses->session_mutex);
		ses->dfs_root_ses = mnt_ctx->root_ses;
		mutex_unlock(&ses->session_mutex);
	}
	return rc;
}

static void set_root_ses(struct cifs_mount_ctx *mnt_ctx)
{
	if (mnt_ctx->ses) {
		spin_lock(&cifs_tcp_ses_lock);
		mnt_ctx->ses->ses_count++;
		spin_unlock(&cifs_tcp_ses_lock);
		dfs_cache_add_refsrv_session(&mnt_ctx->mount_id, mnt_ctx->ses);
	}
	mnt_ctx->root_ses = mnt_ctx->ses;
}

static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, const char *full_path,
			const struct dfs_cache_tgt_iterator *tit)
{
	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
	struct dfs_info3_param ref = {};
	int rc;

	rc = dfs_cache_get_tgt_referral(ref_path + 1, tit, &ref);
	if (rc)
		return rc;

	rc = dfs_parse_target_referral(full_path + 1, &ref, ctx);
	if (rc)
		goto out;

	cifs_mount_put_conns(mnt_ctx);
	rc = get_session(mnt_ctx, ref_path);
	if (rc)
		goto out;

	if (ref.flags & DFSREF_REFERRAL_SERVER)
		set_root_ses(mnt_ctx);

	rc = -EREMOTE;
	if (ref.flags & DFSREF_STORAGE_SERVER) {
		rc = cifs_mount_get_tcon(mnt_ctx);
		if (rc)
			goto out;

		/* some servers may not advertise referral capability under ref.flags */
		if (!(ref.flags & DFSREF_REFERRAL_SERVER) &&
		    is_tcon_dfs(mnt_ctx->tcon))
			set_root_ses(mnt_ctx);

		rc = cifs_is_path_remote(mnt_ctx);
	}

out:
	free_dfs_info_param(&ref);
	return rc;
}

static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
{
	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
	char *ref_path = NULL, *full_path = NULL;
	struct dfs_cache_tgt_iterator *tit;
	struct TCP_Server_Info *server;
	char *origin_fullpath = NULL;
	int num_links = 0;
	int rc;

	ref_path = dfs_get_path(cifs_sb, ctx->UNC);
	if (IS_ERR(ref_path))
		return PTR_ERR(ref_path);

	full_path = build_unc_path_to_root(ctx, cifs_sb, true);
	if (IS_ERR(full_path)) {
		rc = PTR_ERR(full_path);
		full_path = NULL;
		goto out;
	}

	origin_fullpath = kstrdup(full_path, GFP_KERNEL);
	if (!origin_fullpath) {
		rc = -ENOMEM;
		goto out;
	}

	do {
		struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);

		rc = dfs_get_referral(mnt_ctx, ref_path + 1, NULL, &tl);
		if (rc)
			break;

		tit = dfs_cache_get_tgt_iterator(&tl);
		if (!tit) {
			cifs_dbg(VFS, "%s: dfs referral (%s) with no targets\n", __func__,
				 ref_path + 1);
			rc = -ENOENT;
			dfs_cache_free_tgts(&tl);
			break;
		}

		do {
			rc = get_dfs_conn(mnt_ctx, ref_path, full_path, tit);
			if (!rc)
				break;
			if (rc == -EREMOTE) {
				if (++num_links > MAX_NESTED_LINKS) {
					rc = -ELOOP;
					break;
				}
				kfree(ref_path);
				kfree(full_path);
				ref_path = full_path = NULL;

				full_path = build_unc_path_to_root(ctx, cifs_sb, true);
				if (IS_ERR(full_path)) {
					rc = PTR_ERR(full_path);
					full_path = NULL;
				} else {
					ref_path = dfs_get_path(cifs_sb, full_path);
					if (IS_ERR(ref_path)) {
						rc = PTR_ERR(ref_path);
						ref_path = NULL;
					}
				}
				break;
			}
		} while ((tit = dfs_cache_get_next_tgt(&tl, tit)));
		dfs_cache_free_tgts(&tl);
	} while (rc == -EREMOTE);

	if (!rc) {
		server = mnt_ctx->server;

		mutex_lock(&server->refpath_lock);
		server->origin_fullpath = origin_fullpath;
		server->current_fullpath = server->leaf_fullpath;
		mutex_unlock(&server->refpath_lock);
		origin_fullpath = NULL;
	}

out:
	kfree(origin_fullpath);
	kfree(ref_path);
	kfree(full_path);
	return rc;
}

int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
{
	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
	int rc;

	*isdfs = false;

	rc = get_session(mnt_ctx, NULL);
	if (rc)
		return rc;
	mnt_ctx->root_ses = mnt_ctx->ses;
	/*
	 * If called with 'nodfs' mount option, then skip DFS resolving.  Otherwise unconditionally
	 * try to get an DFS referral (even cached) to determine whether it is an DFS mount.
	 *
	 * Skip prefix path to provide support for DFS referrals from w2k8 servers which don't seem
	 * to respond with PATH_NOT_COVERED to requests that include the prefix.
	 */
	if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) ||
	    dfs_get_referral(mnt_ctx, ctx->UNC + 1, NULL, NULL)) {
		rc = cifs_mount_get_tcon(mnt_ctx);
		if (rc)
			return rc;

		rc = cifs_is_path_remote(mnt_ctx);
		if (!rc || rc != -EREMOTE)
			return rc;
	}

	*isdfs = true;
	set_root_ses(mnt_ctx);

	return __dfs_mount_share(mnt_ctx);
}

/* Update dfs referral path of superblock */
static int update_server_fullpath(struct TCP_Server_Info *server, struct cifs_sb_info *cifs_sb,
				  const char *target)
{
	int rc = 0;
	size_t len = strlen(target);
	char *refpath, *npath;

	if (unlikely(len < 2 || *target != '\\'))
		return -EINVAL;

	if (target[1] == '\\') {
		len += 1;
		refpath = kmalloc(len, GFP_KERNEL);
		if (!refpath)
			return -ENOMEM;

		scnprintf(refpath, len, "%s", target);
	} else {
		len += sizeof("\\");
		refpath = kmalloc(len, GFP_KERNEL);
		if (!refpath)
			return -ENOMEM;

		scnprintf(refpath, len, "\\%s", target);
	}

	npath = dfs_cache_canonical_path(refpath, cifs_sb->local_nls, cifs_remap(cifs_sb));
	kfree(refpath);

	if (IS_ERR(npath)) {
		rc = PTR_ERR(npath);
	} else {
		mutex_lock(&server->refpath_lock);
		kfree(server->leaf_fullpath);
		server->leaf_fullpath = npath;
		mutex_unlock(&server->refpath_lock);
		server->current_fullpath = server->leaf_fullpath;
	}
	return rc;
}

static int target_share_matches_server(struct TCP_Server_Info *server, char *share,
				       bool *target_match)
{
	int rc = 0;
	const char *dfs_host;
	size_t dfs_host_len;

	*target_match = true;
	extract_unc_hostname(share, &dfs_host, &dfs_host_len);

	/* Check if hostnames or addresses match */
	cifs_server_lock(server);
	if (dfs_host_len != strlen(server->hostname) ||
	    strncasecmp(dfs_host, server->hostname, dfs_host_len)) {
		cifs_dbg(FYI, "%s: %.*s doesn't match %s\n", __func__,
			 (int)dfs_host_len, dfs_host, server->hostname);
		rc = match_target_ip(server, dfs_host, dfs_host_len, target_match);
		if (rc)
			cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
	}
	cifs_server_unlock(server);
	return rc;
}

static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
				     struct cifs_sb_info *cifs_sb, char *tree, bool islink,
				     struct dfs_cache_tgt_list *tl)
{
	int rc;
	struct TCP_Server_Info *server = tcon->ses->server;
	const struct smb_version_operations *ops = server->ops;
	struct cifs_ses *root_ses = CIFS_DFS_ROOT_SES(tcon->ses);
	struct cifs_tcon *ipc = root_ses->tcon_ipc;
	char *share = NULL, *prefix = NULL;
	struct dfs_cache_tgt_iterator *tit;
	bool target_match;

	tit = dfs_cache_get_tgt_iterator(tl);
	if (!tit) {
		rc = -ENOENT;
		goto out;
	}

	/* Try to tree connect to all dfs targets */
	for (; tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
		const char *target = dfs_cache_get_tgt_name(tit);
		struct dfs_cache_tgt_list ntl = DFS_CACHE_TGT_LIST_INIT(ntl);

		kfree(share);
		kfree(prefix);
		share = prefix = NULL;

		/* Check if share matches with tcp ses */
		rc = dfs_cache_get_tgt_share(server->current_fullpath + 1, tit, &share, &prefix);
		if (rc) {
			cifs_dbg(VFS, "%s: failed to parse target share: %d\n", __func__, rc);
			break;
		}

		rc = target_share_matches_server(server, share, &target_match);
		if (rc)
			break;
		if (!target_match) {
			rc = -EHOSTUNREACH;
			continue;
		}

		dfs_cache_noreq_update_tgthint(server->current_fullpath + 1, tit);

		if (ipc->need_reconnect) {
			scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
			rc = ops->tree_connect(xid, ipc->ses, tree, ipc, cifs_sb->local_nls);
			cifs_dbg(FYI, "%s: reconnect ipc: %d\n", __func__, rc);
		}

		scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
		if (!islink) {
			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
			break;
		}
		/*
		 * If no dfs referrals were returned from link target, then just do a TREE_CONNECT
		 * to it.  Otherwise, cache the dfs referral and then mark current tcp ses for
		 * reconnect so either the demultiplex thread or the echo worker will reconnect to
		 * newly resolved target.
		 */
		if (dfs_cache_find(xid, root_ses, cifs_sb->local_nls, cifs_remap(cifs_sb), target,
				   NULL, &ntl)) {
			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
			if (rc)
				continue;

			rc = cifs_update_super_prepath(cifs_sb, prefix);
		} else {
			/* Target is another dfs share */
			rc = update_server_fullpath(server, cifs_sb, target);
			dfs_cache_free_tgts(tl);

			if (!rc) {
				rc = -EREMOTE;
				list_replace_init(&ntl.tl_list, &tl->tl_list);
			} else
				dfs_cache_free_tgts(&ntl);
		}
		break;
	}

out:
	kfree(share);
	kfree(prefix);

	return rc;
}

static int tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
				   struct cifs_sb_info *cifs_sb, char *tree, bool islink,
				   struct dfs_cache_tgt_list *tl)
{
	int rc;
	int num_links = 0;
	struct TCP_Server_Info *server = tcon->ses->server;
	char *old_fullpath = server->leaf_fullpath;

	do {
		rc = __tree_connect_dfs_target(xid, tcon, cifs_sb, tree, islink, tl);
		if (!rc || rc != -EREMOTE)
			break;
	} while (rc = -ELOOP, ++num_links < MAX_NESTED_LINKS);
	/*
	 * If we couldn't tree connect to any targets from last referral path, then
	 * retry it from newly resolved dfs referral.
	 */
	if (rc && server->leaf_fullpath != old_fullpath)
		cifs_signal_cifsd_for_reconnect(server, true);

	dfs_cache_free_tgts(tl);
	return rc;
}

int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const struct nls_table *nlsc)
{
	int rc;
	struct TCP_Server_Info *server = tcon->ses->server;
	const struct smb_version_operations *ops = server->ops;
	struct super_block *sb = NULL;
	struct cifs_sb_info *cifs_sb;
	struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
	char *tree;
	struct dfs_info3_param ref = {0};

	/* only send once per connect */
	spin_lock(&tcon->tc_lock);
	if (tcon->ses->ses_status != SES_GOOD ||
	    (tcon->status != TID_NEW &&
	    tcon->status != TID_NEED_TCON)) {
		spin_unlock(&tcon->tc_lock);
		return 0;
	}
	tcon->status = TID_IN_TCON;
	spin_unlock(&tcon->tc_lock);

	tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
	if (!tree) {
		rc = -ENOMEM;
		goto out;
	}

	if (tcon->ipc) {
		cifs_server_lock(server);
		scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
		cifs_server_unlock(server);
		rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
		goto out;
	}

	sb = cifs_get_tcp_super(server);
	if (IS_ERR(sb)) {
		rc = PTR_ERR(sb);
		cifs_dbg(VFS, "%s: could not find superblock: %d\n", __func__, rc);
		goto out;
	}

	cifs_sb = CIFS_SB(sb);

	/* If it is not dfs or there was no cached dfs referral, then reconnect to same share */
	if (!server->current_fullpath ||
	    dfs_cache_noreq_find(server->current_fullpath + 1, &ref, &tl)) {
		rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name, tcon, cifs_sb->local_nls);
		goto out;
	}

	rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, ref.server_type == DFS_TYPE_LINK,
				     &tl);
	free_dfs_info_param(&ref);

out:
	kfree(tree);
	cifs_put_tcp_super(sb);

	if (rc) {
		spin_lock(&tcon->tc_lock);
		if (tcon->status == TID_IN_TCON)
			tcon->status = TID_NEED_TCON;
		spin_unlock(&tcon->tc_lock);
	} else {
		spin_lock(&tcon->tc_lock);
		if (tcon->status == TID_IN_TCON)
			tcon->status = TID_GOOD;
		spin_unlock(&tcon->tc_lock);
		tcon->need_reconnect = false;
	}

	return rc;
}