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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 "dfs.h"
25#include "fs_context.h"
26
27static LIST_HEAD(cifs_dfs_automount_list);
28
29static void cifs_dfs_expire_automounts(struct work_struct *work);
30static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
31 cifs_dfs_expire_automounts);
32static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
33
34static void cifs_dfs_expire_automounts(struct work_struct *work)
35{
36 struct list_head *list = &cifs_dfs_automount_list;
37
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);
42}
43
44void cifs_dfs_release_automount_timer(void)
45{
46 BUG_ON(!list_empty(&cifs_dfs_automount_list));
47 cancel_delayed_work_sync(&cifs_dfs_automount_task);
48}
49
50/**
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)
54 *
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.
58 *
59 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
60 * for freeing the returned string.
61 */
62char *
63cifs_build_devname(char *nodename, const char *prepath)
64{
65 size_t pplen;
66 size_t unclen;
67 char *dev;
68 char *pos;
69
70 /* skip over any preceding delimiters */
71 nodename += strspn(nodename, "\\");
72 if (!*nodename)
73 return ERR_PTR(-EINVAL);
74
75 /* get length of UNC and set pos to last char */
76 unclen = strlen(nodename);
77 pos = nodename + unclen - 1;
78
79 /* trim off any trailing delimiters */
80 while (*pos == '\\') {
81 --pos;
82 --unclen;
83 }
84
85 /* allocate a buffer:
86 * +2 for preceding "//"
87 * +1 for delimiter between UNC and prepath
88 * +1 for trailing NULL
89 */
90 pplen = prepath ? strlen(prepath) : 0;
91 dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
92 if (!dev)
93 return ERR_PTR(-ENOMEM);
94
95 pos = dev;
96 /* add the initial "//" */
97 *pos = '/';
98 ++pos;
99 *pos = '/';
100 ++pos;
101
102 /* copy in the UNC portion from referral */
103 memcpy(pos, nodename, unclen);
104 pos += unclen;
105
106 /* copy the prefixpath remainder (if there is one) */
107 if (pplen) {
108 *pos = '/';
109 ++pos;
110 memcpy(pos, prepath, pplen);
111 pos += pplen;
112 }
113
114 /* NULL terminator */
115 *pos = '\0';
116
117 convert_delimiter(dev, '/');
118 return dev;
119}
120
121static int set_dest_addr(struct smb3_fs_context *ctx, const char *full_path)
122{
123 struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;
124 int rc;
125
126 rc = dns_resolve_server_name_to_ip(full_path, addr, NULL);
127 if (!rc)
128 cifs_set_port(addr, ctx->port);
129 return rc;
130}
131
132/*
133 * Create a vfsmount that we can automount
134 */
135static struct vfsmount *cifs_dfs_do_automount(struct path *path)
136{
137 int rc;
138 struct dentry *mntpt = path->dentry;
139 struct fs_context *fc;
140 struct cifs_sb_info *cifs_sb;
141 void *page = NULL;
142 struct smb3_fs_context *ctx, *cur_ctx;
143 struct smb3_fs_context tmp;
144 char *full_path;
145 struct vfsmount *mnt;
146
147 if (IS_ROOT(mntpt))
148 return ERR_PTR(-ESTALE);
149
150 /*
151 * The MSDFS spec states that paths in DFS referral requests and
152 * responses must be prefixed by a single '\' character instead of
153 * the double backslashes usually used in the UNC. This function
154 * gives us the latter, so we must adjust the result.
155 */
156 cifs_sb = CIFS_SB(mntpt->d_sb);
157 if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
158 return ERR_PTR(-EREMOTE);
159
160 cur_ctx = cifs_sb->ctx;
161
162 fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, mntpt);
163 if (IS_ERR(fc))
164 return ERR_CAST(fc);
165
166 ctx = smb3_fc2context(fc);
167
168 page = alloc_dentry_path();
169 full_path = dfs_get_automount_devname(mntpt, page);
170 if (IS_ERR(full_path)) {
171 mnt = ERR_CAST(full_path);
172 goto out;
173 }
174
175 convert_delimiter(full_path, '/');
176 cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
177
178 tmp = *cur_ctx;
179 tmp.source = full_path;
180 tmp.leaf_fullpath = NULL;
181 tmp.UNC = tmp.prepath = NULL;
182
183 rc = smb3_fs_context_dup(ctx, &tmp);
184 if (rc) {
185 mnt = ERR_PTR(rc);
186 goto out;
187 }
188
189 rc = set_dest_addr(ctx, full_path);
190 if (rc) {
191 mnt = ERR_PTR(rc);
192 goto out;
193 }
194
195 rc = smb3_parse_devname(full_path, ctx);
196 if (!rc)
197 mnt = fc_mount(fc);
198 else
199 mnt = ERR_PTR(rc);
200
201out:
202 put_fs_context(fc);
203 free_dentry_path(page);
204 return mnt;
205}
206
207/*
208 * Attempt to automount the referral
209 */
210struct vfsmount *cifs_dfs_d_automount(struct path *path)
211{
212 struct vfsmount *newmnt;
213
214 cifs_dbg(FYI, "%s: %pd\n", __func__, path->dentry);
215
216 newmnt = cifs_dfs_do_automount(path);
217 if (IS_ERR(newmnt)) {
218 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
219 return newmnt;
220 }
221
222 mntget(newmnt); /* prevent immediate expiration */
223 mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
224 schedule_delayed_work(&cifs_dfs_automount_task,
225 cifs_dfs_mountpoint_expiry_timeout);
226 cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
227 return newmnt;
228}
229
230const struct inode_operations cifs_dfs_referral_inode_operations = {
231};
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#include "cifs_unicode.h"
28
29static LIST_HEAD(cifs_dfs_automount_list);
30
31static void cifs_dfs_expire_automounts(struct work_struct *work);
32static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
33 cifs_dfs_expire_automounts);
34static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
35
36static void cifs_dfs_expire_automounts(struct work_struct *work)
37{
38 struct list_head *list = &cifs_dfs_automount_list;
39
40 mark_mounts_for_expiry(list);
41 if (!list_empty(list))
42 schedule_delayed_work(&cifs_dfs_automount_task,
43 cifs_dfs_mountpoint_expiry_timeout);
44}
45
46void cifs_dfs_release_automount_timer(void)
47{
48 BUG_ON(!list_empty(&cifs_dfs_automount_list));
49 cancel_delayed_work_sync(&cifs_dfs_automount_task);
50}
51
52/**
53 * cifs_build_devname - build a devicename from a UNC and optional prepath
54 * @nodename: pointer to UNC string
55 * @prepath: pointer to prefixpath (or NULL if there isn't one)
56 *
57 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
58 * big enough to hold the final thing. Copy the UNC from the nodename, and
59 * concatenate the prepath onto the end of it if there is one.
60 *
61 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
62 * for freeing the returned string.
63 */
64static char *
65cifs_build_devname(char *nodename, const char *prepath)
66{
67 size_t pplen;
68 size_t unclen;
69 char *dev;
70 char *pos;
71
72 /* skip over any preceding delimiters */
73 nodename += strspn(nodename, "\\");
74 if (!*nodename)
75 return ERR_PTR(-EINVAL);
76
77 /* get length of UNC and set pos to last char */
78 unclen = strlen(nodename);
79 pos = nodename + unclen - 1;
80
81 /* trim off any trailing delimiters */
82 while (*pos == '\\') {
83 --pos;
84 --unclen;
85 }
86
87 /* allocate a buffer:
88 * +2 for preceding "//"
89 * +1 for delimiter between UNC and prepath
90 * +1 for trailing NULL
91 */
92 pplen = prepath ? strlen(prepath) : 0;
93 dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
94 if (!dev)
95 return ERR_PTR(-ENOMEM);
96
97 pos = dev;
98 /* add the initial "//" */
99 *pos = '/';
100 ++pos;
101 *pos = '/';
102 ++pos;
103
104 /* copy in the UNC portion from referral */
105 memcpy(pos, nodename, unclen);
106 pos += unclen;
107
108 /* copy the prefixpath remainder (if there is one) */
109 if (pplen) {
110 *pos = '/';
111 ++pos;
112 memcpy(pos, prepath, pplen);
113 pos += pplen;
114 }
115
116 /* NULL terminator */
117 *pos = '\0';
118
119 convert_delimiter(dev, '/');
120 return dev;
121}
122
123
124/**
125 * cifs_compose_mount_options - creates mount options for refferral
126 * @sb_mountdata: parent/root DFS mount options (template)
127 * @fullpath: full path in UNC format
128 * @ref: server's referral
129 * @devname: pointer for saving device name
130 *
131 * creates mount options for submount based on template options sb_mountdata
132 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
133 *
134 * Returns: pointer to new mount options or ERR_PTR.
135 * Caller is responcible for freeing retunrned value if it is not error.
136 */
137char *cifs_compose_mount_options(const char *sb_mountdata,
138 const char *fullpath,
139 const struct dfs_info3_param *ref,
140 char **devname)
141{
142 int rc;
143 char *mountdata = NULL;
144 const char *prepath = NULL;
145 int md_len;
146 char *tkn_e;
147 char *srvIP = NULL;
148 char sep = ',';
149 int off, noff;
150
151 if (sb_mountdata == NULL)
152 return ERR_PTR(-EINVAL);
153
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 *devname = cifs_build_devname(ref->node_name, prepath);
162 if (IS_ERR(*devname)) {
163 rc = PTR_ERR(*devname);
164 *devname = NULL;
165 goto compose_mount_options_err;
166 }
167
168 rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
169 if (rc < 0) {
170 cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
171 __func__, *devname, rc);
172 goto compose_mount_options_err;
173 }
174
175 /*
176 * In most cases, we'll be building a shorter string than the original,
177 * but we do have to assume that the address in the ip= option may be
178 * much longer than the original. Add the max length of an address
179 * string to the length of the original string to allow for worst case.
180 */
181 md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
182 mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
183 if (mountdata == NULL) {
184 rc = -ENOMEM;
185 goto compose_mount_options_err;
186 }
187
188 /* copy all options except of unc,ip,prefixpath */
189 off = 0;
190 if (strncmp(sb_mountdata, "sep=", 4) == 0) {
191 sep = sb_mountdata[4];
192 strncpy(mountdata, sb_mountdata, 5);
193 off += 5;
194 }
195
196 do {
197 tkn_e = strchr(sb_mountdata + off, sep);
198 if (tkn_e == NULL)
199 noff = strlen(sb_mountdata + off);
200 else
201 noff = tkn_e - (sb_mountdata + off) + 1;
202
203 if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
204 off += noff;
205 continue;
206 }
207 if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
208 off += noff;
209 continue;
210 }
211 if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
212 off += noff;
213 continue;
214 }
215 strncat(mountdata, sb_mountdata + off, noff);
216 off += noff;
217 } while (tkn_e);
218 strcat(mountdata, sb_mountdata + off);
219 mountdata[md_len] = '\0';
220
221 /* copy new IP and ref share name */
222 if (mountdata[strlen(mountdata) - 1] != sep)
223 strncat(mountdata, &sep, 1);
224 strcat(mountdata, "ip=");
225 strcat(mountdata, srvIP);
226
227 /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
228 /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
229
230compose_mount_options_out:
231 kfree(srvIP);
232 return mountdata;
233
234compose_mount_options_err:
235 kfree(mountdata);
236 mountdata = ERR_PTR(rc);
237 kfree(*devname);
238 *devname = NULL;
239 goto compose_mount_options_out;
240}
241
242/**
243 * cifs_dfs_do_refmount - mounts specified path using provided refferal
244 * @cifs_sb: parent/root superblock
245 * @fullpath: full path in UNC format
246 * @ref: server's referral
247 */
248static struct vfsmount *cifs_dfs_do_refmount(struct dentry *mntpt,
249 struct cifs_sb_info *cifs_sb,
250 const char *fullpath, const struct dfs_info3_param *ref)
251{
252 struct vfsmount *mnt;
253 char *mountdata;
254 char *devname = NULL;
255
256 /* strip first '\' from fullpath */
257 mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
258 fullpath + 1, ref, &devname);
259
260 if (IS_ERR(mountdata))
261 return (struct vfsmount *)mountdata;
262
263 mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
264 kfree(mountdata);
265 kfree(devname);
266 return mnt;
267
268}
269
270static void dump_referral(const struct dfs_info3_param *ref)
271{
272 cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
273 cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
274 cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
275 ref->flags, ref->server_type);
276 cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
277 ref->ref_flag, ref->path_consumed);
278}
279
280/*
281 * Create a vfsmount that we can automount
282 */
283static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
284{
285 struct dfs_info3_param *referrals = NULL;
286 unsigned int num_referrals = 0;
287 struct cifs_sb_info *cifs_sb;
288 struct cifs_ses *ses;
289 char *full_path;
290 unsigned int xid;
291 int i;
292 int rc;
293 struct vfsmount *mnt;
294 struct tcon_link *tlink;
295
296 cifs_dbg(FYI, "in %s\n", __func__);
297 BUG_ON(IS_ROOT(mntpt));
298
299 /*
300 * The MSDFS spec states that paths in DFS referral requests and
301 * responses must be prefixed by a single '\' character instead of
302 * the double backslashes usually used in the UNC. This function
303 * gives us the latter, so we must adjust the result.
304 */
305 mnt = ERR_PTR(-ENOMEM);
306
307 /* always use tree name prefix */
308 full_path = build_path_from_dentry_optional_prefix(mntpt, true);
309 if (full_path == NULL)
310 goto cdda_exit;
311
312 cifs_sb = CIFS_SB(mntpt->d_sb);
313 tlink = cifs_sb_tlink(cifs_sb);
314 if (IS_ERR(tlink)) {
315 mnt = ERR_CAST(tlink);
316 goto free_full_path;
317 }
318 ses = tlink_tcon(tlink)->ses;
319
320 xid = get_xid();
321 rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
322 &num_referrals, &referrals,
323 cifs_remap(cifs_sb));
324 free_xid(xid);
325
326 cifs_put_tlink(tlink);
327
328 mnt = ERR_PTR(-ENOENT);
329 for (i = 0; i < num_referrals; i++) {
330 int len;
331 dump_referral(referrals + i);
332 /* connect to a node */
333 len = strlen(referrals[i].node_name);
334 if (len < 2) {
335 cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
336 __func__, referrals[i].node_name);
337 mnt = ERR_PTR(-EINVAL);
338 break;
339 }
340 mnt = cifs_dfs_do_refmount(mntpt, cifs_sb,
341 full_path, referrals + i);
342 cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n",
343 __func__, referrals[i].node_name, mnt);
344 if (!IS_ERR(mnt))
345 goto success;
346 }
347
348 /* no valid submounts were found; return error from get_dfs_path() by
349 * preference */
350 if (rc != 0)
351 mnt = ERR_PTR(rc);
352
353success:
354 free_dfs_info_array(referrals, num_referrals);
355free_full_path:
356 kfree(full_path);
357cdda_exit:
358 cifs_dbg(FYI, "leaving %s\n" , __func__);
359 return mnt;
360}
361
362/*
363 * Attempt to automount the referral
364 */
365struct vfsmount *cifs_dfs_d_automount(struct path *path)
366{
367 struct vfsmount *newmnt;
368
369 cifs_dbg(FYI, "in %s\n", __func__);
370
371 newmnt = cifs_dfs_do_automount(path->dentry);
372 if (IS_ERR(newmnt)) {
373 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
374 return newmnt;
375 }
376
377 mntget(newmnt); /* prevent immediate expiration */
378 mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
379 schedule_delayed_work(&cifs_dfs_automount_task,
380 cifs_dfs_mountpoint_expiry_timeout);
381 cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
382 return newmnt;
383}
384
385const struct inode_operations cifs_dfs_referral_inode_operations = {
386};