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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (c) 2022 Paulo Alcantara <palcantara@suse.de>
4 */
5
6#include "cifsproto.h"
7#include "cifs_debug.h"
8#include "dns_resolve.h"
9#include "fs_context.h"
10#include "dfs.h"
11
12/**
13 * dfs_parse_target_referral - set fs context for dfs target referral
14 *
15 * @full_path: full path in UNC format.
16 * @ref: dfs referral pointer.
17 * @ctx: smb3 fs context pointer.
18 *
19 * Return zero if dfs referral was parsed correctly, otherwise non-zero.
20 */
21int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
22 struct smb3_fs_context *ctx)
23{
24 int rc;
25 const char *prepath = NULL;
26 char *path;
27
28 if (!full_path || !*full_path || !ref || !ctx)
29 return -EINVAL;
30
31 if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
32 return -EINVAL;
33
34 if (strlen(full_path) - ref->path_consumed) {
35 prepath = full_path + ref->path_consumed;
36 /* skip initial delimiter */
37 if (*prepath == '/' || *prepath == '\\')
38 prepath++;
39 }
40
41 path = cifs_build_devname(ref->node_name, prepath);
42 if (IS_ERR(path))
43 return PTR_ERR(path);
44
45 rc = smb3_parse_devname(path, ctx);
46 if (rc)
47 goto out;
48
49 rc = dns_resolve_server_name_to_ip(path, (struct sockaddr *)&ctx->dstaddr, NULL);
50
51out:
52 kfree(path);
53 return rc;
54}
55
56static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
57{
58 struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
59 int rc;
60
61 ctx->leaf_fullpath = (char *)full_path;
62 rc = cifs_mount_get_session(mnt_ctx);
63 ctx->leaf_fullpath = NULL;
64
65 return rc;
66}
67
68/*
69 * Get an active reference of @ses so that next call to cifs_put_tcon() won't
70 * release it as any new DFS referrals must go through its IPC tcon.
71 */
72static void set_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
73{
74 struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
75 struct cifs_ses *ses = mnt_ctx->ses;
76
77 if (ses) {
78 spin_lock(&cifs_tcp_ses_lock);
79 cifs_smb_ses_inc_refcount(ses);
80 spin_unlock(&cifs_tcp_ses_lock);
81 }
82 ctx->dfs_root_ses = ses;
83}
84
85static inline int parse_dfs_target(struct smb3_fs_context *ctx,
86 struct dfs_ref_walk *rw,
87 struct dfs_info3_param *tgt)
88{
89 int rc;
90 const char *fpath = ref_walk_fpath(rw) + 1;
91
92 rc = ref_walk_get_tgt(rw, tgt);
93 if (!rc)
94 rc = dfs_parse_target_referral(fpath, tgt, ctx);
95 return rc;
96}
97
98static int setup_dfs_ref(struct cifs_mount_ctx *mnt_ctx,
99 struct dfs_info3_param *tgt,
100 struct dfs_ref_walk *rw)
101{
102 struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
103 struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
104 char *ref_path, *full_path;
105 int rc;
106
107 full_path = smb3_fs_context_fullpath(ctx, CIFS_DIR_SEP(cifs_sb));
108 if (IS_ERR(full_path))
109 return PTR_ERR(full_path);
110
111 if (!tgt || (tgt->server_type == DFS_TYPE_LINK &&
112 DFS_INTERLINK(tgt->flags)))
113 ref_path = dfs_get_path(cifs_sb, ctx->UNC);
114 else
115 ref_path = dfs_get_path(cifs_sb, full_path);
116 if (IS_ERR(ref_path)) {
117 rc = PTR_ERR(ref_path);
118 kfree(full_path);
119 return rc;
120 }
121 ref_walk_path(rw) = ref_path;
122 ref_walk_fpath(rw) = full_path;
123 ref_walk_ses(rw) = ctx->dfs_root_ses;
124 return 0;
125}
126
127static int __dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx,
128 struct dfs_ref_walk *rw)
129{
130 struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
131 struct dfs_info3_param tgt = {};
132 int rc = -ENOENT;
133
134again:
135 do {
136 ctx->dfs_root_ses = ref_walk_ses(rw);
137 if (ref_walk_empty(rw)) {
138 rc = dfs_get_referral(mnt_ctx, ref_walk_path(rw) + 1,
139 NULL, ref_walk_tl(rw));
140 if (rc) {
141 rc = cifs_mount_get_tcon(mnt_ctx);
142 if (!rc)
143 rc = cifs_is_path_remote(mnt_ctx);
144 continue;
145 }
146 if (!ref_walk_num_tgts(rw)) {
147 rc = -ENOENT;
148 continue;
149 }
150 }
151
152 while (ref_walk_next_tgt(rw)) {
153 rc = parse_dfs_target(ctx, rw, &tgt);
154 if (rc)
155 continue;
156
157 cifs_mount_put_conns(mnt_ctx);
158 rc = get_session(mnt_ctx, ref_walk_path(rw));
159 if (rc)
160 continue;
161
162 ref_walk_set_tgt_hint(rw);
163 if (tgt.flags & DFSREF_STORAGE_SERVER) {
164 rc = cifs_mount_get_tcon(mnt_ctx);
165 if (!rc)
166 rc = cifs_is_path_remote(mnt_ctx);
167 if (!rc)
168 break;
169 if (rc != -EREMOTE)
170 continue;
171 }
172
173 set_root_smb_session(mnt_ctx);
174 rc = ref_walk_advance(rw);
175 if (!rc) {
176 rc = setup_dfs_ref(mnt_ctx, &tgt, rw);
177 if (!rc) {
178 rc = -EREMOTE;
179 goto again;
180 }
181 }
182 if (rc != -ELOOP)
183 goto out;
184 }
185 } while (rc && ref_walk_descend(rw));
186
187out:
188 free_dfs_info_param(&tgt);
189 return rc;
190}
191
192static int dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx,
193 struct dfs_ref_walk **rw)
194{
195 int rc;
196
197 *rw = ref_walk_alloc();
198 if (IS_ERR(*rw)) {
199 rc = PTR_ERR(*rw);
200 *rw = NULL;
201 return rc;
202 }
203
204 ref_walk_init(*rw);
205 rc = setup_dfs_ref(mnt_ctx, NULL, *rw);
206 if (!rc)
207 rc = __dfs_referral_walk(mnt_ctx, *rw);
208 return rc;
209}
210
211static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
212{
213 struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
214 struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
215 struct dfs_ref_walk *rw = NULL;
216 struct cifs_tcon *tcon;
217 char *origin_fullpath;
218 int rc;
219
220 origin_fullpath = dfs_get_path(cifs_sb, ctx->source);
221 if (IS_ERR(origin_fullpath))
222 return PTR_ERR(origin_fullpath);
223
224 rc = dfs_referral_walk(mnt_ctx, &rw);
225 if (!rc) {
226 /*
227 * Prevent superblock from being created with any missing
228 * connections.
229 */
230 if (WARN_ON(!mnt_ctx->server))
231 rc = -EHOSTDOWN;
232 else if (WARN_ON(!mnt_ctx->ses))
233 rc = -EACCES;
234 else if (WARN_ON(!mnt_ctx->tcon))
235 rc = -ENOENT;
236 }
237 if (rc)
238 goto out;
239
240 tcon = mnt_ctx->tcon;
241 spin_lock(&tcon->tc_lock);
242 tcon->origin_fullpath = origin_fullpath;
243 origin_fullpath = NULL;
244 ref_walk_set_tcon(rw, tcon);
245 spin_unlock(&tcon->tc_lock);
246 queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
247 dfs_cache_get_ttl() * HZ);
248
249out:
250 kfree(origin_fullpath);
251 ref_walk_free(rw);
252 return rc;
253}
254
255/*
256 * If @ctx->dfs_automount, then update @ctx->dstaddr earlier with the DFS root
257 * server from where we'll start following any referrals. Otherwise rely on the
258 * value provided by mount(2) as the user might not have dns_resolver key set up
259 * and therefore failing to upcall to resolve UNC hostname under @ctx->source.
260 */
261static int update_fs_context_dstaddr(struct smb3_fs_context *ctx)
262{
263 struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;
264 int rc = 0;
265
266 if (!ctx->nodfs && ctx->dfs_automount) {
267 rc = dns_resolve_server_name_to_ip(ctx->source, addr, NULL);
268 if (!rc)
269 cifs_set_port(addr, ctx->port);
270 ctx->dfs_automount = false;
271 }
272 return rc;
273}
274
275int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
276{
277 struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
278 bool nodfs = ctx->nodfs;
279 int rc;
280
281 rc = update_fs_context_dstaddr(ctx);
282 if (rc)
283 return rc;
284
285 rc = get_session(mnt_ctx, NULL);
286 if (rc)
287 return rc;
288
289 /*
290 * If called with 'nodfs' mount option, then skip DFS resolving. Otherwise unconditionally
291 * try to get an DFS referral (even cached) to determine whether it is an DFS mount.
292 *
293 * Skip prefix path to provide support for DFS referrals from w2k8 servers which don't seem
294 * to respond with PATH_NOT_COVERED to requests that include the prefix.
295 */
296 if (!nodfs) {
297 rc = dfs_get_referral(mnt_ctx, ctx->UNC + 1, NULL, NULL);
298 if (rc) {
299 cifs_dbg(FYI, "%s: no dfs referral for %s: %d\n",
300 __func__, ctx->UNC + 1, rc);
301 cifs_dbg(FYI, "%s: assuming non-dfs mount...\n", __func__);
302 nodfs = true;
303 }
304 }
305 if (nodfs) {
306 rc = cifs_mount_get_tcon(mnt_ctx);
307 if (!rc)
308 rc = cifs_is_path_remote(mnt_ctx);
309 return rc;
310 }
311
312 if (!ctx->dfs_conn) {
313 ctx->dfs_conn = true;
314 cifs_mount_put_conns(mnt_ctx);
315 rc = get_session(mnt_ctx, NULL);
316 }
317 if (!rc) {
318 set_root_smb_session(mnt_ctx);
319 rc = __dfs_mount_share(mnt_ctx);
320 }
321 return rc;
322}
323
324static int target_share_matches_server(struct TCP_Server_Info *server, char *share,
325 bool *target_match)
326{
327 int rc = 0;
328 const char *dfs_host;
329 size_t dfs_host_len;
330
331 *target_match = true;
332 extract_unc_hostname(share, &dfs_host, &dfs_host_len);
333
334 /* Check if hostnames or addresses match */
335 cifs_server_lock(server);
336 if (dfs_host_len != strlen(server->hostname) ||
337 strncasecmp(dfs_host, server->hostname, dfs_host_len)) {
338 cifs_dbg(FYI, "%s: %.*s doesn't match %s\n", __func__,
339 (int)dfs_host_len, dfs_host, server->hostname);
340 rc = match_target_ip(server, dfs_host, dfs_host_len, target_match);
341 if (rc)
342 cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
343 }
344 cifs_server_unlock(server);
345 return rc;
346}
347
348static int tree_connect_dfs_target(const unsigned int xid,
349 struct cifs_tcon *tcon,
350 struct cifs_sb_info *cifs_sb,
351 char *tree, bool islink,
352 struct dfs_cache_tgt_list *tl)
353{
354 const struct smb_version_operations *ops = tcon->ses->server->ops;
355 struct TCP_Server_Info *server = tcon->ses->server;
356 struct dfs_cache_tgt_iterator *tit;
357 char *share = NULL, *prefix = NULL;
358 bool target_match;
359 int rc = -ENOENT;
360
361 /* Try to tree connect to all dfs targets */
362 for (tit = dfs_cache_get_tgt_iterator(tl);
363 tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
364 kfree(share);
365 kfree(prefix);
366 share = prefix = NULL;
367
368 /* Check if share matches with tcp ses */
369 rc = dfs_cache_get_tgt_share(server->leaf_fullpath + 1, tit, &share, &prefix);
370 if (rc) {
371 cifs_dbg(VFS, "%s: failed to parse target share: %d\n", __func__, rc);
372 break;
373 }
374
375 rc = target_share_matches_server(server, share, &target_match);
376 if (rc)
377 break;
378 if (!target_match) {
379 rc = -EHOSTUNREACH;
380 continue;
381 }
382
383 dfs_cache_noreq_update_tgthint(server->leaf_fullpath + 1, tit);
384 scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
385 rc = ops->tree_connect(xid, tcon->ses, tree,
386 tcon, tcon->ses->local_nls);
387 if (islink && !rc && cifs_sb)
388 rc = cifs_update_super_prepath(cifs_sb, prefix);
389 break;
390 }
391
392 kfree(share);
393 kfree(prefix);
394 dfs_cache_free_tgts(tl);
395 return rc;
396}
397
398int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon)
399{
400 int rc;
401 struct TCP_Server_Info *server = tcon->ses->server;
402 const struct smb_version_operations *ops = server->ops;
403 DFS_CACHE_TGT_LIST(tl);
404 struct cifs_sb_info *cifs_sb = NULL;
405 struct super_block *sb = NULL;
406 struct dfs_info3_param ref = {0};
407 char *tree;
408
409 /* only send once per connect */
410 spin_lock(&tcon->tc_lock);
411
412 /* if tcon is marked for needing reconnect, update state */
413 if (tcon->need_reconnect)
414 tcon->status = TID_NEED_TCON;
415
416 if (tcon->status == TID_GOOD) {
417 spin_unlock(&tcon->tc_lock);
418 return 0;
419 }
420
421 if (tcon->status != TID_NEW &&
422 tcon->status != TID_NEED_TCON) {
423 spin_unlock(&tcon->tc_lock);
424 return -EHOSTDOWN;
425 }
426
427 tcon->status = TID_IN_TCON;
428 spin_unlock(&tcon->tc_lock);
429
430 tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
431 if (!tree) {
432 rc = -ENOMEM;
433 goto out;
434 }
435
436 if (tcon->ipc) {
437 cifs_server_lock(server);
438 scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
439 cifs_server_unlock(server);
440 rc = ops->tree_connect(xid, tcon->ses, tree,
441 tcon, tcon->ses->local_nls);
442 goto out;
443 }
444
445 sb = cifs_get_dfs_tcon_super(tcon);
446 if (!IS_ERR(sb))
447 cifs_sb = CIFS_SB(sb);
448
449 /* Tree connect to last share in @tcon->tree_name if no DFS referral */
450 if (!server->leaf_fullpath ||
451 dfs_cache_noreq_find(server->leaf_fullpath + 1, &ref, &tl)) {
452 rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name,
453 tcon, tcon->ses->local_nls);
454 goto out;
455 }
456
457 rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, ref.server_type == DFS_TYPE_LINK,
458 &tl);
459 free_dfs_info_param(&ref);
460
461out:
462 kfree(tree);
463 cifs_put_tcp_super(sb);
464
465 if (rc) {
466 spin_lock(&tcon->tc_lock);
467 if (tcon->status == TID_IN_TCON)
468 tcon->status = TID_NEED_TCON;
469 spin_unlock(&tcon->tc_lock);
470 } else {
471 spin_lock(&tcon->tc_lock);
472 if (tcon->status == TID_IN_TCON)
473 tcon->status = TID_GOOD;
474 tcon->need_reconnect = false;
475 spin_unlock(&tcon->tc_lock);
476 }
477
478 return rc;
479}