1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * V9FS FID Management
4 *
5 * Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
6 * Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
7 */
8
9 #include <linux/module.h>
10 #include <linux/errno.h>
11 #include <linux/fs.h>
12 #include <linux/slab.h>
13 #include <linux/sched.h>
14 #include <net/9p/9p.h>
15 #include <net/9p/client.h>
16
17 #include "v9fs.h"
18 #include "v9fs_vfs.h"
19 #include "fid.h"
20
21 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
22 {
23 hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
24 }
25
26
27 /**
28 * v9fs_fid_add - add a fid to a dentry
29 * @dentry: dentry that the fid is being added to
30 * @pfid: fid to add, NULLed out
31 *
32 */
33 void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid)
34 {
35 struct p9_fid *fid = *pfid;
36
37 spin_lock(&dentry->d_lock);
38 __add_fid(dentry, fid);
39 spin_unlock(&dentry->d_lock);
40
41 *pfid = NULL;
42 }
43
44 static bool v9fs_is_writeable(int mode)
45 {
46 if (mode & (P9_OWRITE|P9_ORDWR))
47 return true;
48 else
49 return false;
50 }
51
52 /**
53 * v9fs_fid_find_inode - search for an open fid off of the inode list
54 * @inode: return a fid pointing to a specific inode
55 * @want_writeable: only consider fids which are writeable
56 * @uid: return a fid belonging to the specified user
57 * @any: ignore uid as a selection criteria
58 *
59 */
60 struct p9_fid *v9fs_fid_find_inode(struct inode *inode, bool want_writeable,
61 kuid_t uid, bool any)
62 {
63 struct hlist_head *h;
64 struct p9_fid *fid, *ret = NULL;
65
66 p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode);
67
68 spin_lock(&inode->i_lock);
69 h = (struct hlist_head *)&inode->i_private;
70 hlist_for_each_entry(fid, h, ilist) {
71 if (any || uid_eq(fid->uid, uid)) {
72 if (want_writeable && !v9fs_is_writeable(fid->mode)) {
73 p9_debug(P9_DEBUG_VFS, " mode: %x not writeable?\n",
74 fid->mode);
75 continue;
76 }
77 p9_fid_get(fid);
78 ret = fid;
79 break;
80 }
81 }
82 spin_unlock(&inode->i_lock);
83 return ret;
84 }
85
86 /**
87 * v9fs_open_fid_add - add an open fid to an inode
88 * @inode: inode that the fid is being added to
89 * @pfid: fid to add, NULLed out
90 *
91 */
92
93 void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
94 {
95 struct p9_fid *fid = *pfid;
96
97 spin_lock(&inode->i_lock);
98 hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
99 spin_unlock(&inode->i_lock);
100
101 *pfid = NULL;
102 }
103
104
105 /**
106 * v9fs_fid_find - retrieve a fid that belongs to the specified uid
107 * @dentry: dentry to look for fid in
108 * @uid: return fid that belongs to the specified user
109 * @any: if non-zero, return any fid associated with the dentry
110 *
111 */
112
113 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
114 {
115 struct p9_fid *fid, *ret;
116
117 p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",
118 dentry, dentry, from_kuid(&init_user_ns, uid),
119 any);
120 ret = NULL;
121 /* we'll recheck under lock if there's anything to look in */
122 if (dentry->d_fsdata) {
123 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
124
125 spin_lock(&dentry->d_lock);
126 hlist_for_each_entry(fid, h, dlist) {
127 if (any || uid_eq(fid->uid, uid)) {
128 ret = fid;
129 p9_fid_get(ret);
130 break;
131 }
132 }
133 spin_unlock(&dentry->d_lock);
134 } else {
135 if (dentry->d_inode)
136 ret = v9fs_fid_find_inode(dentry->d_inode, false, uid, any);
137 }
138
139 return ret;
140 }
141
142 /*
143 * We need to hold v9ses->rename_sem as long as we hold references
144 * to returned path array. Array element contain pointers to
145 * dentry names.
146 */
147 static int build_path_from_dentry(struct v9fs_session_info *v9ses,
148 struct dentry *dentry, const unsigned char ***names)
149 {
150 int n = 0, i;
151 const unsigned char **wnames;
152 struct dentry *ds;
153
154 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
155 n++;
156
157 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
158 if (!wnames)
159 goto err_out;
160
161 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
162 wnames[i] = ds->d_name.name;
163
164 *names = wnames;
165 return n;
166 err_out:
167 return -ENOMEM;
168 }
169
170 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
171 kuid_t uid, int any)
172 {
173 struct dentry *ds;
174 const unsigned char **wnames, *uname;
175 int i, n, l, access;
176 struct v9fs_session_info *v9ses;
177 struct p9_fid *fid, *root_fid, *old_fid;
178
179 v9ses = v9fs_dentry2v9ses(dentry);
180 access = v9ses->flags & V9FS_ACCESS_MASK;
181 fid = v9fs_fid_find(dentry, uid, any);
182 if (fid)
183 return fid;
184 /*
185 * we don't have a matching fid. To do a TWALK we need
186 * parent fid. We need to prevent rename when we want to
187 * look at the parent.
188 */
189 down_read(&v9ses->rename_sem);
190 ds = dentry->d_parent;
191 fid = v9fs_fid_find(ds, uid, any);
192 if (fid) {
193 /* Found the parent fid do a lookup with that */
194 old_fid = fid;
195
196 fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1);
197 p9_fid_put(old_fid);
198 goto fid_out;
199 }
200 up_read(&v9ses->rename_sem);
201
202 /* start from the root and try to do a lookup */
203 root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
204 if (!root_fid) {
205 /* the user is not attached to the fs yet */
206 if (access == V9FS_ACCESS_SINGLE)
207 return ERR_PTR(-EPERM);
208
209 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
210 uname = NULL;
211 else
212 uname = v9ses->uname;
213
214 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
215 v9ses->aname);
216 if (IS_ERR(fid))
217 return fid;
218
219 root_fid = p9_fid_get(fid);
220 v9fs_fid_add(dentry->d_sb->s_root, &fid);
221 }
222 /* If we are root ourself just return that */
223 if (dentry->d_sb->s_root == dentry)
224 return root_fid;
225
226 /*
227 * Do a multipath walk with attached root.
228 * When walking parent we need to make sure we
229 * don't have a parallel rename happening
230 */
231 down_read(&v9ses->rename_sem);
232 n = build_path_from_dentry(v9ses, dentry, &wnames);
233 if (n < 0) {
234 fid = ERR_PTR(n);
235 goto err_out;
236 }
237 fid = root_fid;
238 old_fid = root_fid;
239 i = 0;
240 while (i < n) {
241 l = min(n - i, P9_MAXWELEM);
242 /*
243 * We need to hold rename lock when doing a multipath
244 * walk to ensure none of the path components change
245 */
246 fid = p9_client_walk(old_fid, l, &wnames[i],
247 old_fid == root_fid /* clone */);
248 /* non-cloning walk will return the same fid */
249 if (fid != old_fid) {
250 p9_fid_put(old_fid);
251 old_fid = fid;
252 }
253 if (IS_ERR(fid)) {
254 kfree(wnames);
255 goto err_out;
256 }
257 i += l;
258 }
259 kfree(wnames);
260 fid_out:
261 if (!IS_ERR(fid)) {
262 spin_lock(&dentry->d_lock);
263 if (d_unhashed(dentry)) {
264 spin_unlock(&dentry->d_lock);
265 p9_fid_put(fid);
266 fid = ERR_PTR(-ENOENT);
267 } else {
268 __add_fid(dentry, fid);
269 p9_fid_get(fid);
270 spin_unlock(&dentry->d_lock);
271 }
272 }
273 err_out:
274 up_read(&v9ses->rename_sem);
275 return fid;
276 }
277
278 /**
279 * v9fs_fid_lookup - lookup for a fid, try to walk if not found
280 * @dentry: dentry to look for fid in
281 *
282 * Look for a fid in the specified dentry for the current user.
283 * If no fid is found, try to create one walking from a fid from the parent
284 * dentry (if it has one), or the root dentry. If the user haven't accessed
285 * the fs yet, attach now and walk from the root.
286 */
287
288 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
289 {
290 kuid_t uid;
291 int any, access;
292 struct v9fs_session_info *v9ses;
293
294 v9ses = v9fs_dentry2v9ses(dentry);
295 access = v9ses->flags & V9FS_ACCESS_MASK;
296 switch (access) {
297 case V9FS_ACCESS_SINGLE:
298 case V9FS_ACCESS_USER:
299 case V9FS_ACCESS_CLIENT:
300 uid = current_fsuid();
301 any = 0;
302 break;
303
304 case V9FS_ACCESS_ANY:
305 uid = v9ses->uid;
306 any = 1;
307 break;
308
309 default:
310 uid = INVALID_UID;
311 any = 0;
312 break;
313 }
314 return v9fs_fid_lookup_with_uid(dentry, uid, any);
315 }
316
317
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