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
cifs_expire_automounts(struct work_struct * work)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
cifs_release_automount_timer(void)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 *
cifs_build_devname(char * nodename,const char * prepath)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 /* Return full path out of a dentry set for automount */
automount_fullpath(struct dentry * dentry,void * page)121 static char *automount_fullpath(struct dentry *dentry, void *page)
122 {
123 struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb);
124 struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
125 size_t len;
126 char *s;
127
128 spin_lock(&tcon->tc_lock);
129 if (!tcon->origin_fullpath) {
130 spin_unlock(&tcon->tc_lock);
131 return build_path_from_dentry_optional_prefix(dentry,
132 page,
133 true);
134 }
135 spin_unlock(&tcon->tc_lock);
136
137 s = dentry_path_raw(dentry, page, PATH_MAX);
138 if (IS_ERR(s))
139 return s;
140 /* for root, we want "" */
141 if (!s[1])
142 s++;
143
144 spin_lock(&tcon->tc_lock);
145 len = strlen(tcon->origin_fullpath);
146 if (s < (char *)page + len) {
147 spin_unlock(&tcon->tc_lock);
148 return ERR_PTR(-ENAMETOOLONG);
149 }
150
151 s -= len;
152 memcpy(s, tcon->origin_fullpath, len);
153 spin_unlock(&tcon->tc_lock);
154 convert_delimiter(s, '/');
155
156 return s;
157 }
158
159 /*
160 * Create a vfsmount that we can automount
161 */
cifs_do_automount(struct path * path)162 static struct vfsmount *cifs_do_automount(struct path *path)
163 {
164 int rc;
165 struct dentry *mntpt = path->dentry;
166 struct fs_context *fc;
167 void *page = NULL;
168 struct smb3_fs_context *ctx, *cur_ctx;
169 struct smb3_fs_context tmp;
170 char *full_path;
171 struct vfsmount *mnt;
172
173 if (IS_ROOT(mntpt))
174 return ERR_PTR(-ESTALE);
175
176 cur_ctx = CIFS_SB(mntpt->d_sb)->ctx;
177
178 fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, mntpt);
179 if (IS_ERR(fc))
180 return ERR_CAST(fc);
181
182 ctx = smb3_fc2context(fc);
183
184 page = alloc_dentry_path();
185 full_path = automount_fullpath(mntpt, page);
186 if (IS_ERR(full_path)) {
187 mnt = ERR_CAST(full_path);
188 goto out;
189 }
190
191 tmp = *cur_ctx;
192 tmp.source = NULL;
193 tmp.leaf_fullpath = NULL;
194 tmp.UNC = tmp.prepath = NULL;
195 tmp.dfs_root_ses = NULL;
196
197 rc = smb3_fs_context_dup(ctx, &tmp);
198 if (rc) {
199 mnt = ERR_PTR(rc);
200 goto out;
201 }
202
203 rc = smb3_parse_devname(full_path, ctx);
204 if (rc) {
205 mnt = ERR_PTR(rc);
206 goto out;
207 }
208
209 ctx->source = smb3_fs_context_fullpath(ctx, '/');
210 if (IS_ERR(ctx->source)) {
211 mnt = ERR_CAST(ctx->source);
212 ctx->source = NULL;
213 goto out;
214 }
215 cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s\n",
216 __func__, ctx->source, ctx->UNC, ctx->prepath);
217
218 mnt = fc_mount(fc);
219 out:
220 put_fs_context(fc);
221 free_dentry_path(page);
222 return mnt;
223 }
224
225 /*
226 * Attempt to automount the referral
227 */
cifs_d_automount(struct path * path)228 struct vfsmount *cifs_d_automount(struct path *path)
229 {
230 struct vfsmount *newmnt;
231
232 cifs_dbg(FYI, "%s: %pd\n", __func__, path->dentry);
233
234 newmnt = cifs_do_automount(path);
235 if (IS_ERR(newmnt)) {
236 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
237 return newmnt;
238 }
239
240 mntget(newmnt); /* prevent immediate expiration */
241 mnt_set_expiry(newmnt, &cifs_automount_list);
242 schedule_delayed_work(&cifs_automount_task,
243 cifs_mountpoint_expiry_timeout);
244 cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
245 return newmnt;
246 }
247
248 const struct inode_operations cifs_namespace_inode_operations = {
249 };
250