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
21static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
22{
23 hlist_add_head(n: &fid->dlist, h: (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 */
33void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid)
34{
35 struct p9_fid *fid = *pfid;
36
37 spin_lock(lock: &dentry->d_lock);
38 __add_fid(dentry, fid);
39 spin_unlock(lock: &dentry->d_lock);
40
41 *pfid = NULL;
42}
43
44static 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 */
60struct 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(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(left: fid->uid, right: uid)) {
72 if (want_writeable && !v9fs_is_writeable(mode: 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(lock: &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
93void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
94{
95 struct p9_fid *fid = *pfid;
96
97 spin_lock(lock: &inode->i_lock);
98 hlist_add_head(n: &fid->ilist, h: (struct hlist_head *)&inode->i_private);
99 spin_unlock(lock: &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
113static 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(lock: &dentry->d_lock);
126 hlist_for_each_entry(fid, h, dlist) {
127 if (any || uid_eq(left: fid->uid, right: uid)) {
128 ret = fid;
129 p9_fid_get(fid: ret);
130 break;
131 }
132 }
133 spin_unlock(lock: &dentry->d_lock);
134 }
135 if (!ret && dentry->d_inode)
136 ret = v9fs_fid_find_inode(inode: dentry->d_inode, want_writeable: false, uid, any);
137
138 return ret;
139}
140
141/*
142 * We need to hold v9ses->rename_sem as long as we hold references
143 * to returned path array. Array element contain pointers to
144 * dentry names.
145 */
146static int build_path_from_dentry(struct v9fs_session_info *v9ses,
147 struct dentry *dentry, const unsigned char ***names)
148{
149 int n = 0, i;
150 const unsigned char **wnames;
151 struct dentry *ds;
152
153 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
154 n++;
155
156 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
157 if (!wnames)
158 goto err_out;
159
160 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
161 wnames[i] = ds->d_name.name;
162
163 *names = wnames;
164 return n;
165err_out:
166 return -ENOMEM;
167}
168
169static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
170 kuid_t uid, int any)
171{
172 struct dentry *ds;
173 const unsigned char **wnames, *uname;
174 int i, n, l, access;
175 struct v9fs_session_info *v9ses;
176 struct p9_fid *fid, *root_fid, *old_fid;
177
178 v9ses = v9fs_dentry2v9ses(dentry);
179 access = v9ses->flags & V9FS_ACCESS_MASK;
180 fid = v9fs_fid_find(dentry, uid, any);
181 if (fid)
182 return fid;
183 /*
184 * we don't have a matching fid. To do a TWALK we need
185 * parent fid. We need to prevent rename when we want to
186 * look at the parent.
187 */
188 down_read(sem: &v9ses->rename_sem);
189 ds = dentry->d_parent;
190 fid = v9fs_fid_find(dentry: ds, uid, any);
191 if (fid) {
192 /* Found the parent fid do a lookup with that */
193 old_fid = fid;
194
195 fid = p9_client_walk(oldfid: old_fid, nwname: 1, wnames: &dentry->d_name.name, clone: 1);
196 p9_fid_put(fid: old_fid);
197 goto fid_out;
198 }
199 up_read(sem: &v9ses->rename_sem);
200
201 /* start from the root and try to do a lookup */
202 root_fid = v9fs_fid_find(dentry: dentry->d_sb->s_root, uid, any);
203 if (!root_fid) {
204 /* the user is not attached to the fs yet */
205 if (access == V9FS_ACCESS_SINGLE)
206 return ERR_PTR(error: -EPERM);
207
208 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
209 uname = NULL;
210 else
211 uname = v9ses->uname;
212
213 fid = p9_client_attach(clnt: v9ses->clnt, NULL, uname, n_uname: uid,
214 aname: v9ses->aname);
215 if (IS_ERR(ptr: fid))
216 return fid;
217
218 root_fid = p9_fid_get(fid);
219 v9fs_fid_add(dentry: dentry->d_sb->s_root, pfid: &fid);
220 }
221 /* If we are root ourself just return that */
222 if (dentry->d_sb->s_root == dentry)
223 return root_fid;
224
225 /*
226 * Do a multipath walk with attached root.
227 * When walking parent we need to make sure we
228 * don't have a parallel rename happening
229 */
230 down_read(sem: &v9ses->rename_sem);
231 n = build_path_from_dentry(v9ses, dentry, names: &wnames);
232 if (n < 0) {
233 fid = ERR_PTR(error: n);
234 goto err_out;
235 }
236 fid = root_fid;
237 old_fid = root_fid;
238 i = 0;
239 while (i < n) {
240 l = min(n - i, P9_MAXWELEM);
241 /*
242 * We need to hold rename lock when doing a multipath
243 * walk to ensure none of the path components change
244 */
245 fid = p9_client_walk(oldfid: old_fid, nwname: l, wnames: &wnames[i],
246 clone: old_fid == root_fid /* clone */);
247 /* non-cloning walk will return the same fid */
248 if (fid != old_fid) {
249 p9_fid_put(fid: old_fid);
250 old_fid = fid;
251 }
252 if (IS_ERR(ptr: fid)) {
253 kfree(objp: wnames);
254 goto err_out;
255 }
256 i += l;
257 }
258 kfree(objp: wnames);
259fid_out:
260 if (!IS_ERR(ptr: fid)) {
261 spin_lock(lock: &dentry->d_lock);
262 if (d_unhashed(dentry)) {
263 spin_unlock(lock: &dentry->d_lock);
264 p9_fid_put(fid);
265 fid = ERR_PTR(error: -ENOENT);
266 } else {
267 __add_fid(dentry, fid);
268 p9_fid_get(fid);
269 spin_unlock(lock: &dentry->d_lock);
270 }
271 }
272err_out:
273 up_read(sem: &v9ses->rename_sem);
274 return fid;
275}
276
277/**
278 * v9fs_fid_lookup - lookup for a fid, try to walk if not found
279 * @dentry: dentry to look for fid in
280 *
281 * Look for a fid in the specified dentry for the current user.
282 * If no fid is found, try to create one walking from a fid from the parent
283 * dentry (if it has one), or the root dentry. If the user haven't accessed
284 * the fs yet, attach now and walk from the root.
285 */
286
287struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
288{
289 kuid_t uid;
290 int any, access;
291 struct v9fs_session_info *v9ses;
292
293 v9ses = v9fs_dentry2v9ses(dentry);
294 access = v9ses->flags & V9FS_ACCESS_MASK;
295 switch (access) {
296 case V9FS_ACCESS_SINGLE:
297 case V9FS_ACCESS_USER:
298 case V9FS_ACCESS_CLIENT:
299 uid = current_fsuid();
300 any = 0;
301 break;
302
303 case V9FS_ACCESS_ANY:
304 uid = v9ses->uid;
305 any = 1;
306 break;
307
308 default:
309 uid = INVALID_UID;
310 any = 0;
311 break;
312 }
313 return v9fs_fid_lookup_with_uid(dentry, uid, any);
314}
315
316

source code of linux/fs/9p/fid.c