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"
27 static LIST_HEAD(cifs_dfs_automount_list);
29 static void cifs_dfs_expire_automounts(struct work_struct *work);
30 static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
31 cifs_dfs_expire_automounts);
32 static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
34 static void cifs_dfs_expire_automounts(struct work_struct *work)
36 struct list_head *list = &cifs_dfs_automount_list;
38 mark_mounts_for_expiry(list);
39 if (!list_empty(list))
40 schedule_delayed_work(&cifs_dfs_automount_task,
41 cifs_dfs_mountpoint_expiry_timeout);
44 void cifs_dfs_release_automount_timer(void)
46 BUG_ON(!list_empty(&cifs_dfs_automount_list));
47 cancel_delayed_work_sync(&cifs_dfs_automount_task);
51 * cifs_build_devname - build a devicename from a UNC and optional prepath
52 * @nodename: pointer to UNC string
53 * @prepath: pointer to prefixpath (or NULL if there isn't one)
55 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
56 * big enough to hold the final thing. Copy the UNC from the nodename, and
57 * concatenate the prepath onto the end of it if there is one.
59 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
60 * for freeing the returned string.
63 cifs_build_devname(char *nodename, const char *prepath)
70 /* skip over any preceding delimiters */
71 nodename += strspn(nodename, "\\");
73 return ERR_PTR(-EINVAL);
75 /* get length of UNC and set pos to last char */
76 unclen = strlen(nodename);
77 pos = nodename + unclen - 1;
79 /* trim off any trailing delimiters */
80 while (*pos == '\\') {
86 * +2 for preceding "//"
87 * +1 for delimiter between UNC and prepath
88 * +1 for trailing NULL
90 pplen = prepath ? strlen(prepath) : 0;
91 dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
93 return ERR_PTR(-ENOMEM);
96 /* add the initial "//" */
102 /* copy in the UNC portion from referral */
103 memcpy(pos, nodename, unclen);
106 /* copy the prefixpath remainder (if there is one) */
110 memcpy(pos, prepath, pplen);
114 /* NULL terminator */
117 convert_delimiter(dev, '/');
123 * cifs_compose_mount_options - creates mount options for referral
124 * @sb_mountdata: parent/root DFS mount options (template)
125 * @fullpath: full path in UNC format
126 * @ref: optional server's referral
128 * creates mount options for submount based on template options sb_mountdata
129 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
131 * Returns: pointer to new mount options or ERR_PTR.
132 * Caller is responsible for freeing returned value if it is not error.
134 char *cifs_compose_mount_options(const char *sb_mountdata,
135 const char *fullpath,
136 const struct dfs_info3_param *ref)
140 char *mountdata = NULL;
141 const char *prepath = NULL;
148 if (sb_mountdata == NULL)
149 return ERR_PTR(-EINVAL);
152 if (strlen(fullpath) - ref->path_consumed) {
153 prepath = fullpath + ref->path_consumed;
154 /* skip initial delimiter */
155 if (*prepath == '/' || *prepath == '\\')
159 name = cifs_build_devname(ref->node_name, prepath);
163 goto compose_mount_options_err;
166 name = cifs_build_devname((char *)fullpath, NULL);
170 goto compose_mount_options_err;
174 rc = dns_resolve_server_name_to_ip(name, &srvIP);
176 cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
178 goto compose_mount_options_err;
182 * In most cases, we'll be building a shorter string than the original,
183 * but we do have to assume that the address in the ip= option may be
184 * much longer than the original. Add the max length of an address
185 * string to the length of the original string to allow for worst case.
187 md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
188 mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
189 if (mountdata == NULL) {
191 goto compose_mount_options_err;
194 /* copy all options except of unc,ip,prefixpath */
196 if (strncmp(sb_mountdata, "sep=", 4) == 0) {
197 sep = sb_mountdata[4];
198 strncpy(mountdata, sb_mountdata, 5);
203 tkn_e = strchr(sb_mountdata + off, sep);
205 noff = strlen(sb_mountdata + off);
207 noff = tkn_e - (sb_mountdata + off) + 1;
209 if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
213 if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
217 if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
221 strncat(mountdata, sb_mountdata + off, noff);
224 strcat(mountdata, sb_mountdata + off);
225 mountdata[md_len] = '\0';
227 /* copy new IP and ref share name */
228 if (mountdata[strlen(mountdata) - 1] != sep)
229 strncat(mountdata, &sep, 1);
230 strcat(mountdata, "ip=");
231 strcat(mountdata, srvIP);
235 /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
236 /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
238 compose_mount_options_out:
242 compose_mount_options_err:
244 mountdata = ERR_PTR(rc);
246 goto compose_mount_options_out;
250 * cifs_dfs_do_mount - mounts specified path using DFS full path
252 * Always pass down @fullpath to smb3_do_mount() so we can use the root server
253 * to perform failover in case we failed to connect to the first target in the
256 * @cifs_sb: parent/root superblock
257 * @fullpath: full path in UNC format
259 static struct vfsmount *cifs_dfs_do_mount(struct dentry *mntpt,
260 struct cifs_sb_info *cifs_sb,
261 const char *fullpath)
263 struct vfsmount *mnt;
267 devname = kstrndup(fullpath, strlen(fullpath), GFP_KERNEL);
269 return ERR_PTR(-ENOMEM);
271 convert_delimiter(devname, '/');
273 /* TODO: change to call fs_context_for_mount(), fill in context directly, call fc_mount */
275 /* See afs_mntpt_do_automount in fs/afs/mntpt.c for an example */
277 /* strip first '\' from fullpath */
278 mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
280 if (IS_ERR(mountdata)) {
282 return (struct vfsmount *)mountdata;
285 mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
292 * Create a vfsmount that we can automount
294 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
296 struct cifs_sb_info *cifs_sb;
297 struct cifs_ses *ses;
298 struct cifs_tcon *tcon;
299 char *full_path, *root_path;
302 struct vfsmount *mnt;
304 cifs_dbg(FYI, "in %s\n", __func__);
305 BUG_ON(IS_ROOT(mntpt));
308 * The MSDFS spec states that paths in DFS referral requests and
309 * responses must be prefixed by a single '\' character instead of
310 * the double backslashes usually used in the UNC. This function
311 * gives us the latter, so we must adjust the result.
313 mnt = ERR_PTR(-ENOMEM);
315 cifs_sb = CIFS_SB(mntpt->d_sb);
316 if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
317 mnt = ERR_PTR(-EREMOTE);
321 /* always use tree name prefix */
322 full_path = build_path_from_dentry_optional_prefix(mntpt, true);
323 if (full_path == NULL)
326 convert_delimiter(full_path, '\\');
328 cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
330 if (!cifs_sb_master_tlink(cifs_sb)) {
331 cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);
335 tcon = cifs_sb_master_tcon(cifs_sb);
337 cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);
341 root_path = kstrdup(tcon->treeName, GFP_KERNEL);
343 mnt = ERR_PTR(-ENOMEM);
346 cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);
352 * If DFS root has been expired, then unconditionally fetch it again to
353 * refresh DFS referral cache.
355 rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
356 root_path + 1, NULL, NULL);
358 rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
359 cifs_remap(cifs_sb), full_path + 1,
370 * OK - we were able to get and cache a referral for @full_path.
372 * Now, pass it down to cifs_mount() and it will retry every available
373 * node server in case of failures - no need to do it here.
375 mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);
376 cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__,
384 cifs_dbg(FYI, "leaving %s\n" , __func__);
389 * Attempt to automount the referral
391 struct vfsmount *cifs_dfs_d_automount(struct path *path)
393 struct vfsmount *newmnt;
395 cifs_dbg(FYI, "in %s\n", __func__);
397 newmnt = cifs_dfs_do_automount(path->dentry);
398 if (IS_ERR(newmnt)) {
399 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
403 mntget(newmnt); /* prevent immediate expiration */
404 mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
405 schedule_delayed_work(&cifs_dfs_automount_task,
406 cifs_dfs_mountpoint_expiry_timeout);
407 cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
411 const struct inode_operations cifs_dfs_referral_inode_operations = {