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 refferral
124 * @sb_mountdata: parent/root DFS mount options (template)
125 * @fullpath: full path in UNC format
126 * @ref: server's referral
127 * @devname: optional pointer for saving device name
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 responcible for freeing retunrned 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);
153 if (strlen(fullpath) - ref->path_consumed) {
154 prepath = fullpath + ref->path_consumed;
155 /* skip initial delimiter */
156 if (*prepath == '/' || *prepath == '\\')
160 name = cifs_build_devname(ref->node_name, prepath);
164 goto compose_mount_options_err;
167 rc = dns_resolve_server_name_to_ip(name, &srvIP);
169 cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
171 goto compose_mount_options_err;
175 * In most cases, we'll be building a shorter string than the original,
176 * but we do have to assume that the address in the ip= option may be
177 * much longer than the original. Add the max length of an address
178 * string to the length of the original string to allow for worst case.
180 md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
181 mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
182 if (mountdata == NULL) {
184 goto compose_mount_options_err;
187 /* copy all options except of unc,ip,prefixpath */
189 if (strncmp(sb_mountdata, "sep=", 4) == 0) {
190 sep = sb_mountdata[4];
191 strncpy(mountdata, sb_mountdata, 5);
196 tkn_e = strchr(sb_mountdata + off, sep);
198 noff = strlen(sb_mountdata + off);
200 noff = tkn_e - (sb_mountdata + off) + 1;
202 if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
206 if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
210 if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
214 strncat(mountdata, sb_mountdata + off, noff);
217 strcat(mountdata, sb_mountdata + off);
218 mountdata[md_len] = '\0';
220 /* copy new IP and ref share name */
221 if (mountdata[strlen(mountdata) - 1] != sep)
222 strncat(mountdata, &sep, 1);
223 strcat(mountdata, "ip=");
224 strcat(mountdata, srvIP);
229 /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
230 /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
232 compose_mount_options_out:
236 compose_mount_options_err:
238 mountdata = ERR_PTR(rc);
240 goto compose_mount_options_out;
244 * cifs_dfs_do_refmount - mounts specified path using provided refferal
245 * @cifs_sb: parent/root superblock
246 * @fullpath: full path in UNC format
247 * @ref: server's referral
249 static struct vfsmount *cifs_dfs_do_refmount(struct dentry *mntpt,
250 struct cifs_sb_info *cifs_sb,
251 const char *fullpath, const struct dfs_info3_param *ref)
253 struct vfsmount *mnt;
258 * Always pass down the DFS full path to smb3_do_mount() so we
259 * can use it later for failover.
261 devname = kstrndup(fullpath, strlen(fullpath), GFP_KERNEL);
263 return ERR_PTR(-ENOMEM);
265 convert_delimiter(devname, '/');
267 /* strip first '\' from fullpath */
268 mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
269 fullpath + 1, ref, NULL);
270 if (IS_ERR(mountdata)) {
272 return (struct vfsmount *)mountdata;
275 mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
281 static void dump_referral(const struct dfs_info3_param *ref)
283 cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
284 cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
285 cifs_dbg(FYI, "DFS: fl: %d, srv_type: %d\n",
286 ref->flags, ref->server_type);
287 cifs_dbg(FYI, "DFS: ref_flags: %d, path_consumed: %d\n",
288 ref->ref_flag, ref->path_consumed);
292 * Create a vfsmount that we can automount
294 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
296 struct dfs_info3_param referral = {0};
297 struct cifs_sb_info *cifs_sb;
298 struct cifs_ses *ses;
299 struct cifs_tcon *tcon;
300 char *full_path, *root_path;
304 struct vfsmount *mnt;
306 cifs_dbg(FYI, "in %s\n", __func__);
307 BUG_ON(IS_ROOT(mntpt));
310 * The MSDFS spec states that paths in DFS referral requests and
311 * responses must be prefixed by a single '\' character instead of
312 * the double backslashes usually used in the UNC. This function
313 * gives us the latter, so we must adjust the result.
315 mnt = ERR_PTR(-ENOMEM);
317 cifs_sb = CIFS_SB(mntpt->d_sb);
318 if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
319 mnt = ERR_PTR(-EREMOTE);
323 /* always use tree name prefix */
324 full_path = build_path_from_dentry_optional_prefix(mntpt, true);
325 if (full_path == NULL)
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 dump_referral(&referral);
372 len = strlen(referral.node_name);
374 cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
375 __func__, referral.node_name);
376 mnt = ERR_PTR(-EINVAL);
380 * cifs_mount() will retry every available node server in case
383 mnt = cifs_dfs_do_refmount(mntpt, cifs_sb, full_path, &referral);
384 cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n", __func__,
385 referral.node_name, mnt);
388 free_dfs_info_param(&referral);
394 cifs_dbg(FYI, "leaving %s\n" , __func__);
399 * Attempt to automount the referral
401 struct vfsmount *cifs_dfs_d_automount(struct path *path)
403 struct vfsmount *newmnt;
405 cifs_dbg(FYI, "in %s\n", __func__);
407 newmnt = cifs_dfs_do_automount(path->dentry);
408 if (IS_ERR(newmnt)) {
409 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
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__);
421 const struct inode_operations cifs_dfs_referral_inode_operations = {