1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Contains mounting routines used for handling traversal via SMB junctions.
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 * Copyright (c) 2023 Paulo Alcantara <palcantara@suse.de>
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 "cifs_debug.h"
23 #include "fs_context.h"
24
25 static LIST_HEAD(cifs_automount_list);
26
27 static void cifs_expire_automounts(struct work_struct *work);
28 static DECLARE_DELAYED_WORK(cifs_automount_task,
29 cifs_expire_automounts);
30 static int cifs_mountpoint_expiry_timeout = 500 * HZ;
31
32 static void cifs_expire_automounts(struct work_struct *work)
33 {
34 struct list_head *list = &cifs_automount_list;
35
36 mark_mounts_for_expiry(list);
37 if (!list_empty(list))
38 schedule_delayed_work(&cifs_automount_task,
39 cifs_mountpoint_expiry_timeout);
40 }
41
42 void cifs_release_automount_timer(void)
43 {
44 if (WARN_ON(!list_empty(&cifs_automount_list)))
45 return;
46 cancel_delayed_work_sync(&cifs_automount_task);
47 }
48
49 /**
50 * cifs_build_devname - build a devicename from a UNC and optional prepath
51 * @nodename: pointer to UNC string
52 * @prepath: pointer to prefixpath (or NULL if there isn't one)
53 *
54 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
55 * big enough to hold the final thing. Copy the UNC from the nodename, and
56 * concatenate the prepath onto the end of it if there is one.
57 *
58 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
59 * for freeing the returned string.
60 */
61 char *
62 cifs_build_devname(char *nodename, const char *prepath)
63 {
64 size_t pplen;
65 size_t unclen;
66 char *dev;
67 char *pos;
68
69 /* skip over any preceding delimiters */
70 nodename += strspn(nodename, "\\");
71 if (!*nodename)
72 return ERR_PTR(-EINVAL);
73
74 /* get length of UNC and set pos to last char */
75 unclen = strlen(nodename);
76 pos = nodename + unclen - 1;
77
78 /* trim off any trailing delimiters */
79 while (*pos == '\\') {
80 --pos;
81 --unclen;
82 }
83
84 /* allocate a buffer:
85 * +2 for preceding "//"
86 * +1 for delimiter between UNC and prepath
87 * +1 for trailing NULL
88 */
89 pplen = prepath ? strlen(prepath) : 0;
90 dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
91 if (!dev)
92 return ERR_PTR(-ENOMEM);
93
94 pos = dev;
95 /* add the initial "//" */
96 *pos = '/';
97 ++pos;
98 *pos = '/';
99 ++pos;
100
101 /* copy in the UNC portion from referral */
102 memcpy(pos, nodename, unclen);
103 pos += unclen;
104
105 /* copy the prefixpath remainder (if there is one) */
106 if (pplen) {
107 *pos = '/';
108 ++pos;
109 memcpy(pos, prepath, pplen);
110 pos += pplen;
111 }
112
113 /* NULL terminator */
114 *pos = '\0';
115
116 convert_delimiter(dev, '/');
117 return dev;
118 }
119
120 static bool is_dfs_mount(struct dentry *dentry)
121 {
122 struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb);
123 struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
124 bool ret;
125
126 spin_lock(&tcon->tc_lock);
127 ret = !!tcon->origin_fullpath;
128 spin_unlock(&tcon->tc_lock);
129 return ret;
130 }
131
132 /* Return full path out of a dentry set for automount */
133 static char *automount_fullpath(struct dentry *dentry, void *page)
134 {
135 struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb);
136 struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
137 size_t len;
138 char *s;
139
140 spin_lock(&tcon->tc_lock);
141 if (!tcon->origin_fullpath) {
142 spin_unlock(&tcon->tc_lock);
143 return build_path_from_dentry_optional_prefix(dentry,
144 page,
145 true);
146 }
147 spin_unlock(&tcon->tc_lock);
148
149 s = dentry_path_raw(dentry, page, PATH_MAX);
150 if (IS_ERR(s))
151 return s;
152 /* for root, we want "" */
153 if (!s[1])
154 s++;
155
156 spin_lock(&tcon->tc_lock);
157 len = strlen(tcon->origin_fullpath);
158 if (s < (char *)page + len) {
159 spin_unlock(&tcon->tc_lock);
160 return ERR_PTR(-ENAMETOOLONG);
161 }
162
163 s -= len;
164 memcpy(s, tcon->origin_fullpath, len);
165 spin_unlock(&tcon->tc_lock);
166 convert_delimiter(s, '/');
167
168 return s;
169 }
170
171 static void fs_context_set_ids(struct smb3_fs_context *ctx)
172 {
173 kuid_t uid = current_fsuid();
174 kgid_t gid = current_fsgid();
175
176 if (ctx->multiuser) {
177 if (!ctx->uid_specified)
178 ctx->linux_uid = uid;
179 if (!ctx->gid_specified)
180 ctx->linux_gid = gid;
181 }
182 if (!ctx->cruid_specified)
183 ctx->cred_uid = uid;
184 }
185
186 /*
187 * Create a vfsmount that we can automount
188 */
189 static struct vfsmount *cifs_do_automount(struct path *path)
190 {
191 int rc;
192 struct dentry *mntpt = path->dentry;
193 struct fs_context *fc;
194 void *page = NULL;
195 struct smb3_fs_context *ctx, *cur_ctx;
196 struct smb3_fs_context tmp;
197 char *full_path;
198 struct vfsmount *mnt;
199
200 if (IS_ROOT(mntpt))
201 return ERR_PTR(-ESTALE);
202
203 cur_ctx = CIFS_SB(mntpt->d_sb)->ctx;
204
205 fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, mntpt);
206 if (IS_ERR(fc))
207 return ERR_CAST(fc);
208
209 ctx = smb3_fc2context(fc);
210
211 page = alloc_dentry_path();
212 full_path = automount_fullpath(mntpt, page);
213 if (IS_ERR(full_path)) {
214 mnt = ERR_CAST(full_path);
215 goto out;
216 }
217
218 tmp = *cur_ctx;
219 tmp.source = NULL;
220 tmp.leaf_fullpath = NULL;
221 tmp.UNC = tmp.prepath = NULL;
222 tmp.dfs_root_ses = NULL;
223 fs_context_set_ids(&tmp);
224
225 rc = smb3_fs_context_dup(ctx, &tmp);
226 if (rc) {
227 mnt = ERR_PTR(rc);
228 goto out;
229 }
230
231 rc = smb3_parse_devname(full_path, ctx);
232 if (rc) {
233 mnt = ERR_PTR(rc);
234 goto out;
235 }
236
237 ctx->source = smb3_fs_context_fullpath(ctx, '/');
238 if (IS_ERR(ctx->source)) {
239 mnt = ERR_CAST(ctx->source);
240 ctx->source = NULL;
241 goto out;
242 }
243 ctx->dfs_automount = is_dfs_mount(mntpt);
244 cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s dfs_automount=%d\n",
245 __func__, ctx->source, ctx->UNC, ctx->prepath, ctx->dfs_automount);
246
247 mnt = fc_mount(fc);
248 out:
249 put_fs_context(fc);
250 free_dentry_path(page);
251 return mnt;
252 }
253
254 /*
255 * Attempt to automount the referral
256 */
257 struct vfsmount *cifs_d_automount(struct path *path)
258 {
259 struct vfsmount *newmnt;
260
261 cifs_dbg(FYI, "%s: %pd\n", __func__, path->dentry);
262
263 newmnt = cifs_do_automount(path);
264 if (IS_ERR(newmnt)) {
265 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
266 return newmnt;
267 }
268
269 mntget(newmnt); /* prevent immediate expiration */
270 mnt_set_expiry(newmnt, &cifs_automount_list);
271 schedule_delayed_work(&cifs_automount_task,
272 cifs_mountpoint_expiry_timeout);
273 cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
274 return newmnt;
275 }
276
277 const struct inode_operations cifs_namespace_inode_operations = {
278 };
279
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