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(&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 */
33void 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
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(&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
93void 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
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(&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 */
147static 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;
166err_out:
167	return -ENOMEM;
168}
169
170static 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);
260fid_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	}
273err_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
288struct 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