1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/fs/nfs/unlink.c
4  *
5  * nfs sillydelete handling
6  *
7  */
8 
9 #include <linux/slab.h>
10 #include <linux/string.h>
11 #include <linux/dcache.h>
12 #include <linux/sunrpc/sched.h>
13 #include <linux/sunrpc/clnt.h>
14 #include <linux/nfs_fs.h>
15 #include <linux/sched.h>
16 #include <linux/wait.h>
17 #include <linux/namei.h>
18 #include <linux/fsnotify.h>
19 
20 #include "internal.h"
21 #include "nfs4_fs.h"
22 #include "iostat.h"
23 #include "delegation.h"
24 
25 #include "nfstrace.h"
26 
27 /**
28  * nfs_free_unlinkdata - release data from a sillydelete operation.
29  * @data: pointer to unlink structure.
30  */
31 static void
nfs_free_unlinkdata(struct nfs_unlinkdata * data)32 nfs_free_unlinkdata(struct nfs_unlinkdata *data)
33 {
34 	put_cred(data->cred);
35 	kfree(data->args.name.name);
36 	kfree(data);
37 }
38 
39 /**
40  * nfs_async_unlink_done - Sillydelete post-processing
41  * @task: rpc_task of the sillydelete
42  * @calldata: pointer to nfs_unlinkdata
43  *
44  * Do the directory attribute update.
45  */
nfs_async_unlink_done(struct rpc_task * task,void * calldata)46 static void nfs_async_unlink_done(struct rpc_task *task, void *calldata)
47 {
48 	struct nfs_unlinkdata *data = calldata;
49 	struct inode *dir = d_inode(data->dentry->d_parent);
50 
51 	trace_nfs_sillyrename_unlink(data, task->tk_status);
52 	if (!NFS_PROTO(dir)->unlink_done(task, dir))
53 		rpc_restart_call_prepare(task);
54 }
55 
56 /**
57  * nfs_async_unlink_release - Release the sillydelete data.
58  * @calldata: struct nfs_unlinkdata to release
59  *
60  * We need to call nfs_put_unlinkdata as a 'tk_release' task since the
61  * rpc_task would be freed too.
62  */
nfs_async_unlink_release(void * calldata)63 static void nfs_async_unlink_release(void *calldata)
64 {
65 	struct nfs_unlinkdata	*data = calldata;
66 	struct dentry *dentry = data->dentry;
67 	struct super_block *sb = dentry->d_sb;
68 
69 	up_read_non_owner(&NFS_I(d_inode(dentry->d_parent))->rmdir_sem);
70 	d_lookup_done(dentry);
71 	nfs_free_unlinkdata(data);
72 	dput(dentry);
73 	nfs_sb_deactive(sb);
74 }
75 
nfs_unlink_prepare(struct rpc_task * task,void * calldata)76 static void nfs_unlink_prepare(struct rpc_task *task, void *calldata)
77 {
78 	struct nfs_unlinkdata *data = calldata;
79 	struct inode *dir = d_inode(data->dentry->d_parent);
80 	NFS_PROTO(dir)->unlink_rpc_prepare(task, data);
81 }
82 
83 static const struct rpc_call_ops nfs_unlink_ops = {
84 	.rpc_call_done = nfs_async_unlink_done,
85 	.rpc_release = nfs_async_unlink_release,
86 	.rpc_call_prepare = nfs_unlink_prepare,
87 };
88 
nfs_do_call_unlink(struct inode * inode,struct nfs_unlinkdata * data)89 static void nfs_do_call_unlink(struct inode *inode, struct nfs_unlinkdata *data)
90 {
91 	struct rpc_message msg = {
92 		.rpc_argp = &data->args,
93 		.rpc_resp = &data->res,
94 		.rpc_cred = data->cred,
95 	};
96 	struct rpc_task_setup task_setup_data = {
97 		.rpc_message = &msg,
98 		.callback_ops = &nfs_unlink_ops,
99 		.callback_data = data,
100 		.workqueue = nfsiod_workqueue,
101 		.flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
102 	};
103 	struct rpc_task *task;
104 	struct inode *dir = d_inode(data->dentry->d_parent);
105 	nfs_sb_active(dir->i_sb);
106 	data->args.fh = NFS_FH(dir);
107 	nfs_fattr_init(data->res.dir_attr);
108 
109 	NFS_PROTO(dir)->unlink_setup(&msg, data->dentry, inode);
110 
111 	task_setup_data.rpc_client = NFS_CLIENT(dir);
112 	task = rpc_run_task(&task_setup_data);
113 	if (!IS_ERR(task))
114 		rpc_put_task_async(task);
115 }
116 
nfs_call_unlink(struct dentry * dentry,struct inode * inode,struct nfs_unlinkdata * data)117 static int nfs_call_unlink(struct dentry *dentry, struct inode *inode, struct nfs_unlinkdata *data)
118 {
119 	struct inode *dir = d_inode(dentry->d_parent);
120 	struct dentry *alias;
121 
122 	down_read_non_owner(&NFS_I(dir)->rmdir_sem);
123 	alias = d_alloc_parallel(dentry->d_parent, &data->args.name, &data->wq);
124 	if (IS_ERR(alias)) {
125 		up_read_non_owner(&NFS_I(dir)->rmdir_sem);
126 		return 0;
127 	}
128 	if (!d_in_lookup(alias)) {
129 		int ret;
130 		void *devname_garbage = NULL;
131 
132 		/*
133 		 * Hey, we raced with lookup... See if we need to transfer
134 		 * the sillyrename information to the aliased dentry.
135 		 */
136 		spin_lock(&alias->d_lock);
137 		if (d_really_is_positive(alias) &&
138 		    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
139 			devname_garbage = alias->d_fsdata;
140 			alias->d_fsdata = data;
141 			alias->d_flags |= DCACHE_NFSFS_RENAMED;
142 			ret = 1;
143 		} else
144 			ret = 0;
145 		spin_unlock(&alias->d_lock);
146 		dput(alias);
147 		up_read_non_owner(&NFS_I(dir)->rmdir_sem);
148 		/*
149 		 * If we'd displaced old cached devname, free it.  At that
150 		 * point dentry is definitely not a root, so we won't need
151 		 * that anymore.
152 		 */
153 		kfree(devname_garbage);
154 		return ret;
155 	}
156 	data->dentry = alias;
157 	nfs_do_call_unlink(inode, data);
158 	return 1;
159 }
160 
161 /**
162  * nfs_async_unlink - asynchronous unlinking of a file
163  * @dentry: parent directory of dentry
164  * @name: name of dentry to unlink
165  */
166 static int
nfs_async_unlink(struct dentry * dentry,const struct qstr * name)167 nfs_async_unlink(struct dentry *dentry, const struct qstr *name)
168 {
169 	struct nfs_unlinkdata *data;
170 	int status = -ENOMEM;
171 	void *devname_garbage = NULL;
172 
173 	data = kzalloc(sizeof(*data), GFP_KERNEL);
174 	if (data == NULL)
175 		goto out;
176 	data->args.name.name = kstrdup(name->name, GFP_KERNEL);
177 	if (!data->args.name.name)
178 		goto out_free;
179 	data->args.name.len = name->len;
180 
181 	data->cred = get_current_cred();
182 	data->res.dir_attr = &data->dir_attr;
183 	init_waitqueue_head(&data->wq);
184 
185 	status = -EBUSY;
186 	spin_lock(&dentry->d_lock);
187 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
188 		goto out_unlock;
189 	dentry->d_flags |= DCACHE_NFSFS_RENAMED;
190 	devname_garbage = dentry->d_fsdata;
191 	dentry->d_fsdata = data;
192 	spin_unlock(&dentry->d_lock);
193 	/*
194 	 * If we'd displaced old cached devname, free it.  At that
195 	 * point dentry is definitely not a root, so we won't need
196 	 * that anymore.
197 	 */
198 	kfree(devname_garbage);
199 	return 0;
200 out_unlock:
201 	spin_unlock(&dentry->d_lock);
202 	put_cred(data->cred);
203 	kfree(data->args.name.name);
204 out_free:
205 	kfree(data);
206 out:
207 	return status;
208 }
209 
210 /**
211  * nfs_complete_unlink - Initialize completion of the sillydelete
212  * @dentry: dentry to delete
213  * @inode: inode
214  *
215  * Since we're most likely to be called by dentry_iput(), we
216  * only use the dentry to find the sillydelete. We then copy the name
217  * into the qstr.
218  */
219 void
nfs_complete_unlink(struct dentry * dentry,struct inode * inode)220 nfs_complete_unlink(struct dentry *dentry, struct inode *inode)
221 {
222 	struct nfs_unlinkdata	*data;
223 
224 	spin_lock(&dentry->d_lock);
225 	dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
226 	data = dentry->d_fsdata;
227 	dentry->d_fsdata = NULL;
228 	spin_unlock(&dentry->d_lock);
229 
230 	if (NFS_STALE(inode) || !nfs_call_unlink(dentry, inode, data))
231 		nfs_free_unlinkdata(data);
232 }
233 
234 /* Cancel a queued async unlink. Called when a sillyrename run fails. */
235 static void
nfs_cancel_async_unlink(struct dentry * dentry)236 nfs_cancel_async_unlink(struct dentry *dentry)
237 {
238 	spin_lock(&dentry->d_lock);
239 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
240 		struct nfs_unlinkdata *data = dentry->d_fsdata;
241 
242 		dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
243 		dentry->d_fsdata = NULL;
244 		spin_unlock(&dentry->d_lock);
245 		nfs_free_unlinkdata(data);
246 		return;
247 	}
248 	spin_unlock(&dentry->d_lock);
249 }
250 
251 /**
252  * nfs_async_rename_done - Sillyrename post-processing
253  * @task: rpc_task of the sillyrename
254  * @calldata: nfs_renamedata for the sillyrename
255  *
256  * Do the directory attribute updates and the d_move
257  */
nfs_async_rename_done(struct rpc_task * task,void * calldata)258 static void nfs_async_rename_done(struct rpc_task *task, void *calldata)
259 {
260 	struct nfs_renamedata *data = calldata;
261 	struct inode *old_dir = data->old_dir;
262 	struct inode *new_dir = data->new_dir;
263 	struct dentry *old_dentry = data->old_dentry;
264 
265 	trace_nfs_sillyrename_rename(old_dir, old_dentry,
266 			new_dir, data->new_dentry, task->tk_status);
267 	if (!NFS_PROTO(old_dir)->rename_done(task, old_dir, new_dir)) {
268 		rpc_restart_call_prepare(task);
269 		return;
270 	}
271 
272 	if (data->complete)
273 		data->complete(task, data);
274 }
275 
276 /**
277  * nfs_async_rename_release - Release the sillyrename data.
278  * @calldata: the struct nfs_renamedata to be released
279  */
nfs_async_rename_release(void * calldata)280 static void nfs_async_rename_release(void *calldata)
281 {
282 	struct nfs_renamedata	*data = calldata;
283 	struct super_block *sb = data->old_dir->i_sb;
284 
285 	if (d_really_is_positive(data->old_dentry))
286 		nfs_mark_for_revalidate(d_inode(data->old_dentry));
287 
288 	/* The result of the rename is unknown. Play it safe by
289 	 * forcing a new lookup */
290 	if (data->cancelled) {
291 		spin_lock(&data->old_dir->i_lock);
292 		nfs_force_lookup_revalidate(data->old_dir);
293 		spin_unlock(&data->old_dir->i_lock);
294 		if (data->new_dir != data->old_dir) {
295 			spin_lock(&data->new_dir->i_lock);
296 			nfs_force_lookup_revalidate(data->new_dir);
297 			spin_unlock(&data->new_dir->i_lock);
298 		}
299 	}
300 
301 	dput(data->old_dentry);
302 	dput(data->new_dentry);
303 	iput(data->old_dir);
304 	iput(data->new_dir);
305 	nfs_sb_deactive(sb);
306 	put_cred(data->cred);
307 	kfree(data);
308 }
309 
nfs_rename_prepare(struct rpc_task * task,void * calldata)310 static void nfs_rename_prepare(struct rpc_task *task, void *calldata)
311 {
312 	struct nfs_renamedata *data = calldata;
313 	NFS_PROTO(data->old_dir)->rename_rpc_prepare(task, data);
314 }
315 
316 static const struct rpc_call_ops nfs_rename_ops = {
317 	.rpc_call_done = nfs_async_rename_done,
318 	.rpc_release = nfs_async_rename_release,
319 	.rpc_call_prepare = nfs_rename_prepare,
320 };
321 
322 /**
323  * nfs_async_rename - perform an asynchronous rename operation
324  * @old_dir: directory that currently holds the dentry to be renamed
325  * @new_dir: target directory for the rename
326  * @old_dentry: original dentry to be renamed
327  * @new_dentry: dentry to which the old_dentry should be renamed
328  * @complete: Function to run on successful completion
329  *
330  * It's expected that valid references to the dentries and inodes are held
331  */
332 struct rpc_task *
nfs_async_rename(struct inode * old_dir,struct inode * new_dir,struct dentry * old_dentry,struct dentry * new_dentry,void (* complete)(struct rpc_task *,struct nfs_renamedata *))333 nfs_async_rename(struct inode *old_dir, struct inode *new_dir,
334 		 struct dentry *old_dentry, struct dentry *new_dentry,
335 		 void (*complete)(struct rpc_task *, struct nfs_renamedata *))
336 {
337 	struct nfs_renamedata *data;
338 	struct rpc_message msg = { };
339 	struct rpc_task_setup task_setup_data = {
340 		.rpc_message = &msg,
341 		.callback_ops = &nfs_rename_ops,
342 		.workqueue = nfsiod_workqueue,
343 		.rpc_client = NFS_CLIENT(old_dir),
344 		.flags = RPC_TASK_ASYNC | RPC_TASK_CRED_NOREF,
345 	};
346 
347 	data = kzalloc(sizeof(*data), GFP_KERNEL);
348 	if (data == NULL)
349 		return ERR_PTR(-ENOMEM);
350 	task_setup_data.callback_data = data;
351 
352 	data->cred = get_current_cred();
353 
354 	msg.rpc_argp = &data->args;
355 	msg.rpc_resp = &data->res;
356 	msg.rpc_cred = data->cred;
357 
358 	/* set up nfs_renamedata */
359 	data->old_dir = old_dir;
360 	ihold(old_dir);
361 	data->new_dir = new_dir;
362 	ihold(new_dir);
363 	data->old_dentry = dget(old_dentry);
364 	data->new_dentry = dget(new_dentry);
365 	nfs_fattr_init(&data->old_fattr);
366 	nfs_fattr_init(&data->new_fattr);
367 	data->complete = complete;
368 
369 	/* set up nfs_renameargs */
370 	data->args.old_dir = NFS_FH(old_dir);
371 	data->args.old_name = &old_dentry->d_name;
372 	data->args.new_dir = NFS_FH(new_dir);
373 	data->args.new_name = &new_dentry->d_name;
374 
375 	/* set up nfs_renameres */
376 	data->res.old_fattr = &data->old_fattr;
377 	data->res.new_fattr = &data->new_fattr;
378 
379 	nfs_sb_active(old_dir->i_sb);
380 
381 	NFS_PROTO(data->old_dir)->rename_setup(&msg, old_dentry, new_dentry);
382 
383 	return rpc_run_task(&task_setup_data);
384 }
385 
386 /*
387  * Perform tasks needed when a sillyrename is done such as cancelling the
388  * queued async unlink if it failed.
389  */
390 static void
nfs_complete_sillyrename(struct rpc_task * task,struct nfs_renamedata * data)391 nfs_complete_sillyrename(struct rpc_task *task, struct nfs_renamedata *data)
392 {
393 	struct dentry *dentry = data->old_dentry;
394 
395 	if (task->tk_status != 0) {
396 		nfs_cancel_async_unlink(dentry);
397 		return;
398 	}
399 }
400 
401 #define SILLYNAME_PREFIX ".nfs"
402 #define SILLYNAME_PREFIX_LEN ((unsigned)sizeof(SILLYNAME_PREFIX) - 1)
403 #define SILLYNAME_FILEID_LEN ((unsigned)sizeof(u64) << 1)
404 #define SILLYNAME_COUNTER_LEN ((unsigned)sizeof(unsigned int) << 1)
405 #define SILLYNAME_LEN (SILLYNAME_PREFIX_LEN + \
406 		SILLYNAME_FILEID_LEN + \
407 		SILLYNAME_COUNTER_LEN)
408 
409 /**
410  * nfs_sillyrename - Perform a silly-rename of a dentry
411  * @dir: inode of directory that contains dentry
412  * @dentry: dentry to be sillyrenamed
413  *
414  * NFSv2/3 is stateless and the server doesn't know when the client is
415  * holding a file open. To prevent application problems when a file is
416  * unlinked while it's still open, the client performs a "silly-rename".
417  * That is, it renames the file to a hidden file in the same directory,
418  * and only performs the unlink once the last reference to it is put.
419  *
420  * The final cleanup is done during dentry_iput.
421  *
422  * (Note: NFSv4 is stateful, and has opens, so in theory an NFSv4 server
423  * could take responsibility for keeping open files referenced.  The server
424  * would also need to ensure that opened-but-deleted files were kept over
425  * reboots.  However, we may not assume a server does so.  (RFC 5661
426  * does provide an OPEN4_RESULT_PRESERVE_UNLINKED flag that a server can
427  * use to advertise that it does this; some day we may take advantage of
428  * it.))
429  */
430 int
nfs_sillyrename(struct inode * dir,struct dentry * dentry)431 nfs_sillyrename(struct inode *dir, struct dentry *dentry)
432 {
433 	static unsigned int sillycounter;
434 	unsigned char silly[SILLYNAME_LEN + 1];
435 	unsigned long long fileid;
436 	struct dentry *sdentry;
437 	struct inode *inode = d_inode(dentry);
438 	struct rpc_task *task;
439 	int            error = -EBUSY;
440 
441 	dfprintk(VFS, "NFS: silly-rename(%pd2, ct=%d)\n",
442 		dentry, d_count(dentry));
443 	nfs_inc_stats(dir, NFSIOS_SILLYRENAME);
444 
445 	/*
446 	 * We don't allow a dentry to be silly-renamed twice.
447 	 */
448 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
449 		goto out;
450 
451 	fileid = NFS_FILEID(d_inode(dentry));
452 
453 	sdentry = NULL;
454 	do {
455 		int slen;
456 		dput(sdentry);
457 		sillycounter++;
458 		slen = scnprintf(silly, sizeof(silly),
459 				SILLYNAME_PREFIX "%0*llx%0*x",
460 				SILLYNAME_FILEID_LEN, fileid,
461 				SILLYNAME_COUNTER_LEN, sillycounter);
462 
463 		dfprintk(VFS, "NFS: trying to rename %pd to %s\n",
464 				dentry, silly);
465 
466 		sdentry = lookup_one_len(silly, dentry->d_parent, slen);
467 		/*
468 		 * N.B. Better to return EBUSY here ... it could be
469 		 * dangerous to delete the file while it's in use.
470 		 */
471 		if (IS_ERR(sdentry))
472 			goto out;
473 	} while (d_inode(sdentry) != NULL); /* need negative lookup */
474 
475 	ihold(inode);
476 
477 	/* queue unlink first. Can't do this from rpc_release as it
478 	 * has to allocate memory
479 	 */
480 	error = nfs_async_unlink(dentry, &sdentry->d_name);
481 	if (error)
482 		goto out_dput;
483 
484 	/* run the rename task, undo unlink if it fails */
485 	task = nfs_async_rename(dir, dir, dentry, sdentry,
486 					nfs_complete_sillyrename);
487 	if (IS_ERR(task)) {
488 		error = -EBUSY;
489 		nfs_cancel_async_unlink(dentry);
490 		goto out_dput;
491 	}
492 
493 	/* wait for the RPC task to complete, unless a SIGKILL intervenes */
494 	error = rpc_wait_for_completion_task(task);
495 	if (error == 0)
496 		error = task->tk_status;
497 	switch (error) {
498 	case 0:
499 		/* The rename succeeded */
500 		nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
501 		spin_lock(&inode->i_lock);
502 		NFS_I(inode)->attr_gencount = nfs_inc_attr_generation_counter();
503 		nfs_set_cache_invalid(inode, NFS_INO_INVALID_CHANGE |
504 						     NFS_INO_INVALID_CTIME |
505 						     NFS_INO_REVAL_FORCED);
506 		spin_unlock(&inode->i_lock);
507 		d_move(dentry, sdentry);
508 		break;
509 	case -ERESTARTSYS:
510 		/* The result of the rename is unknown. Play it safe by
511 		 * forcing a new lookup */
512 		d_drop(dentry);
513 		d_drop(sdentry);
514 	}
515 	rpc_put_task(task);
516 out_dput:
517 	iput(inode);
518 	dput(sdentry);
519 out:
520 	return error;
521 }
522