xref: /openbmc/linux/fs/9p/fid.c (revision 9464bf9762a8b16f4fbd05b115dcde51b339ac58)
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  
__add_fid(struct dentry * dentry,struct p9_fid * fid)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   */
v9fs_fid_add(struct dentry * dentry,struct p9_fid ** pfid)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  
v9fs_is_writeable(int mode)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   */
v9fs_fid_find_inode(struct inode * inode,bool want_writeable,kuid_t uid,bool any)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  
v9fs_open_fid_add(struct inode * inode,struct p9_fid ** pfid)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  
v9fs_fid_find(struct dentry * dentry,kuid_t uid,int any)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  	}
135  	if (!ret && dentry->d_inode)
136  		ret = v9fs_fid_find_inode(dentry->d_inode, 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   */
build_path_from_dentry(struct v9fs_session_info * v9ses,struct dentry * dentry,const unsigned char *** names)146  static 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;
165  err_out:
166  	return -ENOMEM;
167  }
168  
v9fs_fid_lookup_with_uid(struct dentry * dentry,kuid_t uid,int any)169  static 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(&v9ses->rename_sem);
189  	ds = dentry->d_parent;
190  	fid = v9fs_fid_find(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(old_fid, 1, &dentry->d_name.name, 1);
196  		p9_fid_put(old_fid);
197  		goto fid_out;
198  	}
199  	up_read(&v9ses->rename_sem);
200  
201  	/* start from the root and try to do a lookup */
202  	root_fid = v9fs_fid_find(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(-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(v9ses->clnt, NULL, uname, uid,
214  				       v9ses->aname);
215  		if (IS_ERR(fid))
216  			return fid;
217  
218  		root_fid = p9_fid_get(fid);
219  		v9fs_fid_add(dentry->d_sb->s_root, &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(&v9ses->rename_sem);
231  	n  = build_path_from_dentry(v9ses, dentry, &wnames);
232  	if (n < 0) {
233  		fid = ERR_PTR(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(old_fid, l, &wnames[i],
246  				     old_fid == root_fid /* clone */);
247  		/* non-cloning walk will return the same fid */
248  		if (fid != old_fid) {
249  			p9_fid_put(old_fid);
250  			old_fid = fid;
251  		}
252  		if (IS_ERR(fid)) {
253  			kfree(wnames);
254  			goto err_out;
255  		}
256  		i += l;
257  	}
258  	kfree(wnames);
259  fid_out:
260  	if (!IS_ERR(fid)) {
261  		spin_lock(&dentry->d_lock);
262  		if (d_unhashed(dentry)) {
263  			spin_unlock(&dentry->d_lock);
264  			p9_fid_put(fid);
265  			fid = ERR_PTR(-ENOENT);
266  		} else {
267  			__add_fid(dentry, fid);
268  			p9_fid_get(fid);
269  			spin_unlock(&dentry->d_lock);
270  		}
271  	}
272  err_out:
273  	up_read(&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  
v9fs_fid_lookup(struct dentry * dentry)287  struct 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