1 /*
2 * Contains the CIFS DFS referral mounting routines used for handling
3 * traversal via DFS junction point
4 *
5 * Copyright (c) 2007 Igor Mammedov
6 * Copyright (C) International Business Machines Corp., 2008
7 * Author(s): Igor Mammedov (niallain@gmail.com)
8 * Steve French (sfrench@us.ibm.com)
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; either version
12 * 2 of the License, or (at your option) any later version.
13 */
14
15 #include <linux/dcache.h>
16 #include <linux/mount.h>
17 #include <linux/namei.h>
18 #include <linux/slab.h>
19 #include <linux/vfs.h>
20 #include <linux/fs.h>
21 #include <linux/inet.h>
22 #include "cifsglob.h"
23 #include "cifsproto.h"
24 #include "cifsfs.h"
25 #include "dns_resolve.h"
26 #include "cifs_debug.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 refferral
125 * @sb_mountdata: parent/root DFS mount options (template)
126 * @fullpath: full path in UNC format
127 * @ref: server's referral
128 * @devname: pointer for saving device name
129 *
130 * creates mount options for submount based on template options sb_mountdata
131 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
132 *
133 * Returns: pointer to new mount options or ERR_PTR.
134 * Caller is responcible for freeing retunrned value if it is not error.
135 */
cifs_compose_mount_options(const char * sb_mountdata,const char * fullpath,const struct dfs_info3_param * ref,char ** devname)136 char *cifs_compose_mount_options(const char *sb_mountdata,
137 const char *fullpath,
138 const struct dfs_info3_param *ref,
139 char **devname)
140 {
141 int rc;
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 (strlen(fullpath) - ref->path_consumed)
154 prepath = fullpath + ref->path_consumed;
155
156 *devname = cifs_build_devname(ref->node_name, prepath);
157 if (IS_ERR(*devname)) {
158 rc = PTR_ERR(*devname);
159 *devname = NULL;
160 goto compose_mount_options_err;
161 }
162
163 rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
164 if (rc < 0) {
165 cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
166 __func__, *devname, rc);
167 goto compose_mount_options_err;
168 }
169
170 /*
171 * In most cases, we'll be building a shorter string than the original,
172 * but we do have to assume that the address in the ip= option may be
173 * much longer than the original. Add the max length of an address
174 * string to the length of the original string to allow for worst case.
175 */
176 md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
177 mountdata = kzalloc(md_len + 1, GFP_KERNEL);
178 if (mountdata == NULL) {
179 rc = -ENOMEM;
180 goto compose_mount_options_err;
181 }
182
183 /* copy all options except of unc,ip,prefixpath */
184 off = 0;
185 if (strncmp(sb_mountdata, "sep=", 4) == 0) {
186 sep = sb_mountdata[4];
187 strncpy(mountdata, sb_mountdata, 5);
188 off += 5;
189 }
190
191 do {
192 tkn_e = strchr(sb_mountdata + off, sep);
193 if (tkn_e == NULL)
194 noff = strlen(sb_mountdata + off);
195 else
196 noff = tkn_e - (sb_mountdata + off) + 1;
197
198 if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
199 off += noff;
200 continue;
201 }
202 if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
203 off += noff;
204 continue;
205 }
206 if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
207 off += noff;
208 continue;
209 }
210 strncat(mountdata, sb_mountdata + off, noff);
211 off += noff;
212 } while (tkn_e);
213 strcat(mountdata, sb_mountdata + off);
214 mountdata[md_len] = '\0';
215
216 /* copy new IP and ref share name */
217 if (mountdata[strlen(mountdata) - 1] != sep)
218 strncat(mountdata, &sep, 1);
219 strcat(mountdata, "ip=");
220 strcat(mountdata, srvIP);
221
222 /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
223 /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
224
225 compose_mount_options_out:
226 kfree(srvIP);
227 return mountdata;
228
229 compose_mount_options_err:
230 kfree(mountdata);
231 mountdata = ERR_PTR(rc);
232 kfree(*devname);
233 *devname = NULL;
234 goto compose_mount_options_out;
235 }
236
237 /**
238 * cifs_dfs_do_refmount - mounts specified path using provided refferal
239 * @cifs_sb: parent/root superblock
240 * @fullpath: full path in UNC format
241 * @ref: server's referral
242 */
cifs_dfs_do_refmount(struct cifs_sb_info * cifs_sb,const char * fullpath,const struct dfs_info3_param * ref)243 static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
244 const char *fullpath, const struct dfs_info3_param *ref)
245 {
246 struct vfsmount *mnt;
247 char *mountdata;
248 char *devname = NULL;
249
250 /* strip first '\' from fullpath */
251 mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
252 fullpath + 1, ref, &devname);
253
254 if (IS_ERR(mountdata))
255 return (struct vfsmount *)mountdata;
256
257 mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
258 kfree(mountdata);
259 kfree(devname);
260 return mnt;
261
262 }
263
dump_referral(const struct dfs_info3_param * ref)264 static void dump_referral(const struct dfs_info3_param *ref)
265 {
266 cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
267 cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
268 cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
269 ref->flags, ref->server_type);
270 cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
271 ref->ref_flag, ref->path_consumed);
272 }
273
274 /*
275 * Create a vfsmount that we can automount
276 */
cifs_dfs_do_automount(struct dentry * mntpt)277 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
278 {
279 struct dfs_info3_param *referrals = NULL;
280 unsigned int num_referrals = 0;
281 struct cifs_sb_info *cifs_sb;
282 struct cifs_ses *ses;
283 char *full_path;
284 unsigned int xid;
285 int i;
286 int rc;
287 struct vfsmount *mnt;
288 struct tcon_link *tlink;
289
290 cifs_dbg(FYI, "in %s\n", __func__);
291 BUG_ON(IS_ROOT(mntpt));
292
293 /*
294 * The MSDFS spec states that paths in DFS referral requests and
295 * responses must be prefixed by a single '\' character instead of
296 * the double backslashes usually used in the UNC. This function
297 * gives us the latter, so we must adjust the result.
298 */
299 mnt = ERR_PTR(-ENOMEM);
300 full_path = build_path_from_dentry(mntpt);
301 if (full_path == NULL)
302 goto cdda_exit;
303
304 cifs_sb = CIFS_SB(mntpt->d_inode->i_sb);
305 tlink = cifs_sb_tlink(cifs_sb);
306 if (IS_ERR(tlink)) {
307 mnt = ERR_CAST(tlink);
308 goto free_full_path;
309 }
310 ses = tlink_tcon(tlink)->ses;
311
312 xid = get_xid();
313 rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
314 &num_referrals, &referrals,
315 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
316 free_xid(xid);
317
318 cifs_put_tlink(tlink);
319
320 mnt = ERR_PTR(-ENOENT);
321 for (i = 0; i < num_referrals; i++) {
322 int len;
323 dump_referral(referrals + i);
324 /* connect to a node */
325 len = strlen(referrals[i].node_name);
326 if (len < 2) {
327 cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
328 __func__, referrals[i].node_name);
329 mnt = ERR_PTR(-EINVAL);
330 break;
331 }
332 mnt = cifs_dfs_do_refmount(cifs_sb,
333 full_path, referrals + i);
334 cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n",
335 __func__, referrals[i].node_name, mnt);
336 if (!IS_ERR(mnt))
337 goto success;
338 }
339
340 /* no valid submounts were found; return error from get_dfs_path() by
341 * preference */
342 if (rc != 0)
343 mnt = ERR_PTR(rc);
344
345 success:
346 free_dfs_info_array(referrals, num_referrals);
347 free_full_path:
348 kfree(full_path);
349 cdda_exit:
350 cifs_dbg(FYI, "leaving %s\n" , __func__);
351 return mnt;
352 }
353
354 /*
355 * Attempt to automount the referral
356 */
cifs_dfs_d_automount(struct path * path)357 struct vfsmount *cifs_dfs_d_automount(struct path *path)
358 {
359 struct vfsmount *newmnt;
360
361 cifs_dbg(FYI, "in %s\n", __func__);
362
363 newmnt = cifs_dfs_do_automount(path->dentry);
364 if (IS_ERR(newmnt)) {
365 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
366 return newmnt;
367 }
368
369 mntget(newmnt); /* prevent immediate expiration */
370 mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
371 schedule_delayed_work(&cifs_dfs_automount_task,
372 cifs_dfs_mountpoint_expiry_timeout);
373 cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
374 return newmnt;
375 }
376
377 const struct inode_operations cifs_dfs_referral_inode_operations = {
378 };
379