1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Contains the CIFS DFS referral mounting routines used for handling
4 * traversal via DFS junction point
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)
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>
18 #include <linux/inet.h>
20 #include "cifsproto.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"
28 static LIST_HEAD(cifs_dfs_automount_list
);
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
;
35 static void cifs_dfs_expire_automounts(struct work_struct
*work
)
37 struct list_head
*list
= &cifs_dfs_automount_list
;
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
);
45 void cifs_dfs_release_automount_timer(void)
47 BUG_ON(!list_empty(&cifs_dfs_automount_list
));
48 cancel_delayed_work_sync(&cifs_dfs_automount_task
);
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)
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.
60 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
61 * for freeing the returned string.
64 cifs_build_devname(char *nodename
, const char *prepath
)
71 /* skip over any preceding delimiters */
72 nodename
+= strspn(nodename
, "\\");
74 return ERR_PTR(-EINVAL
);
76 /* get length of UNC and set pos to last char */
77 unclen
= strlen(nodename
);
78 pos
= nodename
+ unclen
- 1;
80 /* trim off any trailing delimiters */
81 while (*pos
== '\\') {
87 * +2 for preceding "//"
88 * +1 for delimiter between UNC and prepath
89 * +1 for trailing NULL
91 pplen
= prepath
? strlen(prepath
) : 0;
92 dev
= kmalloc(2 + unclen
+ 1 + pplen
+ 1, GFP_KERNEL
);
94 return ERR_PTR(-ENOMEM
);
97 /* add the initial "//" */
103 /* copy in the UNC portion from referral */
104 memcpy(pos
, nodename
, unclen
);
107 /* copy the prefixpath remainder (if there is one) */
111 memcpy(pos
, prepath
, pplen
);
115 /* NULL terminator */
118 convert_delimiter(dev
, '/');
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
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.
132 * Returns: pointer to new mount options or ERR_PTR.
133 * Caller is responsible for freeing returned value if it is not error.
135 char *cifs_compose_mount_options(const char *sb_mountdata
,
136 const char *fullpath
,
137 const struct dfs_info3_param
*ref
,
142 char *mountdata
= NULL
;
143 const char *prepath
= NULL
;
150 if (sb_mountdata
== NULL
)
151 return ERR_PTR(-EINVAL
);
154 if (strlen(fullpath
) - ref
->path_consumed
) {
155 prepath
= fullpath
+ ref
->path_consumed
;
156 /* skip initial delimiter */
157 if (*prepath
== '/' || *prepath
== '\\')
161 name
= cifs_build_devname(ref
->node_name
, prepath
);
165 goto compose_mount_options_err
;
168 name
= cifs_build_devname((char *)fullpath
, NULL
);
172 goto compose_mount_options_err
;
176 rc
= dns_resolve_server_name_to_ip(name
, &srvIP
);
178 cifs_dbg(FYI
, "%s: Failed to resolve server part of %s to IP: %d\n",
180 goto compose_mount_options_err
;
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.
189 md_len
= strlen(sb_mountdata
) + INET6_ADDRSTRLEN
;
190 mountdata
= kzalloc(md_len
+ sizeof("ip=") + 1, GFP_KERNEL
);
191 if (mountdata
== NULL
) {
193 goto compose_mount_options_err
;
196 /* copy all options except of unc,ip,prefixpath */
198 if (strncmp(sb_mountdata
, "sep=", 4) == 0) {
199 sep
= sb_mountdata
[4];
200 strncpy(mountdata
, sb_mountdata
, 5);
205 tkn_e
= strchr(sb_mountdata
+ off
, sep
);
207 noff
= strlen(sb_mountdata
+ off
);
209 noff
= tkn_e
- (sb_mountdata
+ off
) + 1;
211 if (strncasecmp(sb_mountdata
+ off
, "unc=", 4) == 0) {
215 if (strncasecmp(sb_mountdata
+ off
, "ip=", 3) == 0) {
219 if (strncasecmp(sb_mountdata
+ off
, "prefixpath=", 11) == 0) {
223 strncat(mountdata
, sb_mountdata
+ off
, noff
);
226 strcat(mountdata
, sb_mountdata
+ off
);
227 mountdata
[md_len
] = '\0';
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
);
240 /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
241 /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
243 compose_mount_options_out
:
247 compose_mount_options_err
:
249 mountdata
= ERR_PTR(rc
);
251 goto compose_mount_options_out
;
255 * cifs_dfs_do_mount - mounts specified path using DFS full path
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
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
265 static struct vfsmount
*cifs_dfs_do_mount(struct dentry
*mntpt
,
266 struct cifs_sb_info
*cifs_sb
,
267 const char *fullpath
)
269 struct vfsmount
*mnt
;
273 devname
= kstrndup(fullpath
, strlen(fullpath
), GFP_KERNEL
);
275 return ERR_PTR(-ENOMEM
);
277 convert_delimiter(devname
, '/');
279 /* TODO: change to call fs_context_for_mount(), fill in context directly, call fc_mount */
281 /* See afs_mntpt_do_automount in fs/afs/mntpt.c for an example */
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
)) {
288 return (struct vfsmount
*)mountdata
;
291 mnt
= vfs_submount(mntpt
, &cifs_fs_type
, devname
, mountdata
);
298 * Create a vfsmount that we can automount
300 static struct vfsmount
*cifs_dfs_do_automount(struct dentry
*mntpt
)
302 struct cifs_sb_info
*cifs_sb
;
303 struct cifs_ses
*ses
;
304 struct cifs_tcon
*tcon
;
305 char *full_path
, *root_path
;
308 struct vfsmount
*mnt
;
310 cifs_dbg(FYI
, "in %s\n", __func__
);
311 BUG_ON(IS_ROOT(mntpt
));
314 * The MSDFS spec states that paths in DFS referral requests and
315 * responses must be prefixed by a single '\' character instead of
316 * the double backslashes usually used in the UNC. This function
317 * gives us the latter, so we must adjust the result.
319 mnt
= ERR_PTR(-ENOMEM
);
321 cifs_sb
= CIFS_SB(mntpt
->d_sb
);
322 if (cifs_sb
->mnt_cifs_flags
& CIFS_MOUNT_NO_DFS
) {
323 mnt
= ERR_PTR(-EREMOTE
);
327 /* always use tree name prefix */
328 full_path
= build_path_from_dentry_optional_prefix(mntpt
, true);
329 if (full_path
== NULL
)
332 convert_delimiter(full_path
, '\\');
334 cifs_dbg(FYI
, "%s: full_path: %s\n", __func__
, full_path
);
336 if (!cifs_sb_master_tlink(cifs_sb
)) {
337 cifs_dbg(FYI
, "%s: master tlink is NULL\n", __func__
);
341 tcon
= cifs_sb_master_tcon(cifs_sb
);
343 cifs_dbg(FYI
, "%s: master tcon is NULL\n", __func__
);
347 root_path
= kstrdup(tcon
->treeName
, GFP_KERNEL
);
349 mnt
= ERR_PTR(-ENOMEM
);
352 cifs_dbg(FYI
, "%s: root path: %s\n", __func__
, root_path
);
358 * If DFS root has been expired, then unconditionally fetch it again to
359 * refresh DFS referral cache.
361 rc
= dfs_cache_find(xid
, ses
, cifs_sb
->local_nls
, cifs_remap(cifs_sb
),
362 root_path
+ 1, NULL
, NULL
);
364 rc
= dfs_cache_find(xid
, ses
, cifs_sb
->local_nls
,
365 cifs_remap(cifs_sb
), full_path
+ 1,
376 * OK - we were able to get and cache a referral for @full_path.
378 * Now, pass it down to cifs_mount() and it will retry every available
379 * node server in case of failures - no need to do it here.
381 mnt
= cifs_dfs_do_mount(mntpt
, cifs_sb
, full_path
);
382 cifs_dbg(FYI
, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__
,
390 cifs_dbg(FYI
, "leaving %s\n" , __func__
);
395 * Attempt to automount the referral
397 struct vfsmount
*cifs_dfs_d_automount(struct path
*path
)
399 struct vfsmount
*newmnt
;
401 cifs_dbg(FYI
, "in %s\n", __func__
);
403 newmnt
= cifs_dfs_do_automount(path
->dentry
);
404 if (IS_ERR(newmnt
)) {
405 cifs_dbg(FYI
, "leaving %s [automount failed]\n" , __func__
);
409 mntget(newmnt
); /* prevent immediate expiration */
410 mnt_set_expiry(newmnt
, &cifs_dfs_automount_list
);
411 schedule_delayed_work(&cifs_dfs_automount_task
,
412 cifs_dfs_mountpoint_expiry_timeout
);
413 cifs_dbg(FYI
, "leaving %s [ok]\n" , __func__
);
417 const struct inode_operations cifs_dfs_referral_inode_operations
= {