1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Contains the CIFS DFS referral mounting routines used for handling
4 * traversal via DFS junction point
5 *
6 * Copyright (c) 2007 Igor Mammedov
7 * Copyright (C) International Business Machines Corp., 2008
8 * Author(s): Igor Mammedov (niallain@gmail.com)
9 * Steve French (sfrench@us.ibm.com)
10 */
11
12 #include <linux/dcache.h>
13 #include <linux/mount.h>
14 #include <linux/namei.h>
15 #include <linux/slab.h>
16 #include <linux/vfs.h>
17 #include <linux/fs.h>
18 #include <linux/inet.h>
19 #include "cifsglob.h"
20 #include "cifsproto.h"
21 #include "cifsfs.h"
22 #include "dns_resolve.h"
23 #include "cifs_debug.h"
24 #include "cifs_unicode.h"
25 #include "dfs_cache.h"
26 #include "fs_context.h"
27
28 static LIST_HEAD(cifs_dfs_automount_list);
29
30 static void cifs_dfs_expire_automounts(struct work_struct *work);
31 static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
32 cifs_dfs_expire_automounts);
33 static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
34
cifs_dfs_expire_automounts(struct work_struct * work)35 static void cifs_dfs_expire_automounts(struct work_struct *work)
36 {
37 struct list_head *list = &cifs_dfs_automount_list;
38
39 mark_mounts_for_expiry(list);
40 if (!list_empty(list))
41 schedule_delayed_work(&cifs_dfs_automount_task,
42 cifs_dfs_mountpoint_expiry_timeout);
43 }
44
cifs_dfs_release_automount_timer(void)45 void cifs_dfs_release_automount_timer(void)
46 {
47 BUG_ON(!list_empty(&cifs_dfs_automount_list));
48 cancel_delayed_work_sync(&cifs_dfs_automount_task);
49 }
50
51 /**
52 * cifs_build_devname - build a devicename from a UNC and optional prepath
53 * @nodename: pointer to UNC string
54 * @prepath: pointer to prefixpath (or NULL if there isn't one)
55 *
56 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
57 * big enough to hold the final thing. Copy the UNC from the nodename, and
58 * concatenate the prepath onto the end of it if there is one.
59 *
60 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
61 * for freeing the returned string.
62 */
63 static char *
cifs_build_devname(char * nodename,const char * prepath)64 cifs_build_devname(char *nodename, const char *prepath)
65 {
66 size_t pplen;
67 size_t unclen;
68 char *dev;
69 char *pos;
70
71 /* skip over any preceding delimiters */
72 nodename += strspn(nodename, "\\");
73 if (!*nodename)
74 return ERR_PTR(-EINVAL);
75
76 /* get length of UNC and set pos to last char */
77 unclen = strlen(nodename);
78 pos = nodename + unclen - 1;
79
80 /* trim off any trailing delimiters */
81 while (*pos == '\\') {
82 --pos;
83 --unclen;
84 }
85
86 /* allocate a buffer:
87 * +2 for preceding "//"
88 * +1 for delimiter between UNC and prepath
89 * +1 for trailing NULL
90 */
91 pplen = prepath ? strlen(prepath) : 0;
92 dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
93 if (!dev)
94 return ERR_PTR(-ENOMEM);
95
96 pos = dev;
97 /* add the initial "//" */
98 *pos = '/';
99 ++pos;
100 *pos = '/';
101 ++pos;
102
103 /* copy in the UNC portion from referral */
104 memcpy(pos, nodename, unclen);
105 pos += unclen;
106
107 /* copy the prefixpath remainder (if there is one) */
108 if (pplen) {
109 *pos = '/';
110 ++pos;
111 memcpy(pos, prepath, pplen);
112 pos += pplen;
113 }
114
115 /* NULL terminator */
116 *pos = '\0';
117
118 convert_delimiter(dev, '/');
119 return dev;
120 }
121
122
123 /**
124 * cifs_compose_mount_options - creates mount options for referral
125 * @sb_mountdata: parent/root DFS mount options (template)
126 * @fullpath: full path in UNC format
127 * @ref: optional server's referral
128 *
129 * creates mount options for submount based on template options sb_mountdata
130 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
131 *
132 * Returns: pointer to new mount options or ERR_PTR.
133 * Caller is responsible for freeing returned value if it is not error.
134 */
cifs_compose_mount_options(const char * sb_mountdata,const char * fullpath,const struct dfs_info3_param * ref,char ** devname)135 char *cifs_compose_mount_options(const char *sb_mountdata,
136 const char *fullpath,
137 const struct dfs_info3_param *ref,
138 char **devname)
139 {
140 int rc;
141 char *name;
142 char *mountdata = NULL;
143 const char *prepath = NULL;
144 int md_len;
145 char *tkn_e;
146 char *srvIP = NULL;
147 char sep = ',';
148 int off, noff;
149
150 if (sb_mountdata == NULL)
151 return ERR_PTR(-EINVAL);
152
153 if (ref) {
154 if (strlen(fullpath) - ref->path_consumed) {
155 prepath = fullpath + ref->path_consumed;
156 /* skip initial delimiter */
157 if (*prepath == '/' || *prepath == '\\')
158 prepath++;
159 }
160
161 name = cifs_build_devname(ref->node_name, prepath);
162 if (IS_ERR(name)) {
163 rc = PTR_ERR(name);
164 name = NULL;
165 goto compose_mount_options_err;
166 }
167 } else {
168 name = cifs_build_devname((char *)fullpath, NULL);
169 if (IS_ERR(name)) {
170 rc = PTR_ERR(name);
171 name = NULL;
172 goto compose_mount_options_err;
173 }
174 }
175
176 rc = dns_resolve_server_name_to_ip(name, &srvIP);
177 if (rc < 0) {
178 cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
179 __func__, name, rc);
180 goto compose_mount_options_err;
181 }
182
183 /*
184 * In most cases, we'll be building a shorter string than the original,
185 * but we do have to assume that the address in the ip= option may be
186 * much longer than the original. Add the max length of an address
187 * string to the length of the original string to allow for worst case.
188 */
189 md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
190 mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
191 if (mountdata == NULL) {
192 rc = -ENOMEM;
193 goto compose_mount_options_err;
194 }
195
196 /* copy all options except of unc,ip,prefixpath */
197 off = 0;
198 if (strncmp(sb_mountdata, "sep=", 4) == 0) {
199 sep = sb_mountdata[4];
200 strncpy(mountdata, sb_mountdata, 5);
201 off += 5;
202 }
203
204 do {
205 tkn_e = strchr(sb_mountdata + off, sep);
206 if (tkn_e == NULL)
207 noff = strlen(sb_mountdata + off);
208 else
209 noff = tkn_e - (sb_mountdata + off) + 1;
210
211 if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
212 off += noff;
213 continue;
214 }
215 if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
216 off += noff;
217 continue;
218 }
219 if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
220 off += noff;
221 continue;
222 }
223 strncat(mountdata, sb_mountdata + off, noff);
224 off += noff;
225 } while (tkn_e);
226 strcat(mountdata, sb_mountdata + off);
227 mountdata[md_len] = '\0';
228
229 /* copy new IP and ref share name */
230 if (mountdata[strlen(mountdata) - 1] != sep)
231 strncat(mountdata, &sep, 1);
232 strcat(mountdata, "ip=");
233 strcat(mountdata, srvIP);
234
235 if (devname)
236 *devname = name;
237 else
238 kfree(name);
239
240 /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
241 /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
242
243 compose_mount_options_out:
244 kfree(srvIP);
245 return mountdata;
246
247 compose_mount_options_err:
248 kfree(mountdata);
249 mountdata = ERR_PTR(rc);
250 kfree(name);
251 goto compose_mount_options_out;
252 }
253
254 /**
255 * cifs_dfs_do_mount - mounts specified path using DFS full path
256 *
257 * Always pass down @fullpath to smb3_do_mount() so we can use the root server
258 * to perform failover in case we failed to connect to the first target in the
259 * referral.
260 *
261 * @mntpt: directory entry for the path we are trying to automount
262 * @cifs_sb: parent/root superblock
263 * @fullpath: full path in UNC format
264 */
cifs_dfs_do_mount(struct dentry * mntpt,struct cifs_sb_info * cifs_sb,const char * fullpath)265 static struct vfsmount *cifs_dfs_do_mount(struct dentry *mntpt,
266 struct cifs_sb_info *cifs_sb,
267 const char *fullpath)
268 {
269 struct vfsmount *mnt;
270 char *mountdata;
271 char *devname;
272
273 devname = kstrdup(fullpath, GFP_KERNEL);
274 if (!devname)
275 return ERR_PTR(-ENOMEM);
276
277 convert_delimiter(devname, '/');
278
279 /* TODO: change to call fs_context_for_mount(), fill in context directly, call fc_mount */
280
281 /* See afs_mntpt_do_automount in fs/afs/mntpt.c for an example */
282
283 /* strip first '\' from fullpath */
284 mountdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options,
285 fullpath + 1, NULL, NULL);
286 if (IS_ERR(mountdata)) {
287 kfree(devname);
288 return (struct vfsmount *)mountdata;
289 }
290
291 mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
292 kfree(mountdata);
293 kfree(devname);
294 return mnt;
295 }
296
297 /*
298 * Create a vfsmount that we can automount
299 */
cifs_dfs_do_automount(struct dentry * mntpt)300 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
301 {
302 struct cifs_sb_info *cifs_sb;
303 struct cifs_ses *ses;
304 struct cifs_tcon *tcon;
305 void *page;
306 char *full_path, *root_path;
307 unsigned int xid;
308 int rc;
309 struct vfsmount *mnt;
310
311 cifs_dbg(FYI, "in %s\n", __func__);
312 BUG_ON(IS_ROOT(mntpt));
313
314 /*
315 * The MSDFS spec states that paths in DFS referral requests and
316 * responses must be prefixed by a single '\' character instead of
317 * the double backslashes usually used in the UNC. This function
318 * gives us the latter, so we must adjust the result.
319 */
320 mnt = ERR_PTR(-ENOMEM);
321
322 cifs_sb = CIFS_SB(mntpt->d_sb);
323 if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
324 mnt = ERR_PTR(-EREMOTE);
325 goto cdda_exit;
326 }
327
328 page = alloc_dentry_path();
329 /* always use tree name prefix */
330 full_path = build_path_from_dentry_optional_prefix(mntpt, page, true);
331 if (IS_ERR(full_path)) {
332 mnt = ERR_CAST(full_path);
333 goto free_full_path;
334 }
335
336 convert_delimiter(full_path, '\\');
337
338 cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
339
340 if (!cifs_sb_master_tlink(cifs_sb)) {
341 cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);
342 goto free_full_path;
343 }
344
345 tcon = cifs_sb_master_tcon(cifs_sb);
346 if (!tcon) {
347 cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);
348 goto free_full_path;
349 }
350
351 root_path = kstrdup(tcon->treeName, GFP_KERNEL);
352 if (!root_path) {
353 mnt = ERR_PTR(-ENOMEM);
354 goto free_full_path;
355 }
356 cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);
357
358 ses = tcon->ses;
359 xid = get_xid();
360
361 /*
362 * If DFS root has been expired, then unconditionally fetch it again to
363 * refresh DFS referral cache.
364 */
365 rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
366 root_path + 1, NULL, NULL);
367 if (!rc) {
368 rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
369 cifs_remap(cifs_sb), full_path + 1,
370 NULL, NULL);
371 }
372
373 free_xid(xid);
374
375 if (rc) {
376 mnt = ERR_PTR(rc);
377 goto free_root_path;
378 }
379 /*
380 * OK - we were able to get and cache a referral for @full_path.
381 *
382 * Now, pass it down to cifs_mount() and it will retry every available
383 * node server in case of failures - no need to do it here.
384 */
385 mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);
386 cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__,
387 full_path + 1, mnt);
388
389 free_root_path:
390 kfree(root_path);
391 free_full_path:
392 free_dentry_path(page);
393 cdda_exit:
394 cifs_dbg(FYI, "leaving %s\n" , __func__);
395 return mnt;
396 }
397
398 /*
399 * Attempt to automount the referral
400 */
cifs_dfs_d_automount(struct path * path)401 struct vfsmount *cifs_dfs_d_automount(struct path *path)
402 {
403 struct vfsmount *newmnt;
404
405 cifs_dbg(FYI, "in %s\n", __func__);
406
407 newmnt = cifs_dfs_do_automount(path->dentry);
408 if (IS_ERR(newmnt)) {
409 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
410 return newmnt;
411 }
412
413 mntget(newmnt); /* prevent immediate expiration */
414 mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
415 schedule_delayed_work(&cifs_dfs_automount_task,
416 cifs_dfs_mountpoint_expiry_timeout);
417 cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
418 return newmnt;
419 }
420
421 const struct inode_operations cifs_dfs_referral_inode_operations = {
422 };
423