[thirdparty/kernel/linux.git] / fs / fuse / passthrough.c

// SPDX-License-Identifier: GPL-2.0
/*
 * FUSE passthrough to backing file.
 *
 * Copyright (c) 2023 CTERA Networks.
 */

#include "fuse_i.h"

#include <linux/file.h>
#include <linux/backing-file.h>
#include <linux/splice.h>

static void fuse_file_accessed(struct file *file)
{
	struct inode *inode = file_inode(file);

	fuse_invalidate_atime(inode);
}

static void fuse_file_modified(struct file *file)
{
	struct inode *inode = file_inode(file);

	fuse_invalidate_attr_mask(inode, FUSE_STATX_MODSIZE);
}

ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
	struct file *file = iocb->ki_filp;
	struct fuse_file *ff = file->private_data;
	struct file *backing_file = fuse_file_passthrough(ff);
	size_t count = iov_iter_count(iter);
	ssize_t ret;
	struct backing_file_ctx ctx = {
		.cred = ff->cred,
		.user_file = file,
		.accessed = fuse_file_accessed,
	};


	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu\n", __func__,
		 backing_file, iocb->ki_pos, count);

	if (!count)
		return 0;

	ret = backing_file_read_iter(backing_file, iter, iocb, iocb->ki_flags,
				     &ctx);

	return ret;
}

ssize_t fuse_passthrough_write_iter(struct kiocb *iocb,
				    struct iov_iter *iter)
{
	struct file *file = iocb->ki_filp;
	struct inode *inode = file_inode(file);
	struct fuse_file *ff = file->private_data;
	struct file *backing_file = fuse_file_passthrough(ff);
	size_t count = iov_iter_count(iter);
	ssize_t ret;
	struct backing_file_ctx ctx = {
		.cred = ff->cred,
		.user_file = file,
		.end_write = fuse_file_modified,
	};

	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu\n", __func__,
		 backing_file, iocb->ki_pos, count);

	if (!count)
		return 0;

	inode_lock(inode);
	ret = backing_file_write_iter(backing_file, iter, iocb, iocb->ki_flags,
				      &ctx);
	inode_unlock(inode);

	return ret;
}

ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos,
				     struct pipe_inode_info *pipe,
				     size_t len, unsigned int flags)
{
	struct fuse_file *ff = in->private_data;
	struct file *backing_file = fuse_file_passthrough(ff);
	struct backing_file_ctx ctx = {
		.cred = ff->cred,
		.user_file = in,
		.accessed = fuse_file_accessed,
	};

	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
		 backing_file, ppos ? *ppos : 0, len, flags);

	return backing_file_splice_read(backing_file, ppos, pipe, len, flags,
					&ctx);
}

ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
				      struct file *out, loff_t *ppos,
				      size_t len, unsigned int flags)
{
	struct fuse_file *ff = out->private_data;
	struct file *backing_file = fuse_file_passthrough(ff);
	struct inode *inode = file_inode(out);
	ssize_t ret;
	struct backing_file_ctx ctx = {
		.cred = ff->cred,
		.user_file = out,
		.end_write = fuse_file_modified,
	};

	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
		 backing_file, ppos ? *ppos : 0, len, flags);

	inode_lock(inode);
	ret = backing_file_splice_write(pipe, backing_file, ppos, len, flags,
					&ctx);
	inode_unlock(inode);

	return ret;
}

struct fuse_backing *fuse_backing_get(struct fuse_backing *fb)
{
	if (fb && refcount_inc_not_zero(&fb->count))
		return fb;
	return NULL;
}

static void fuse_backing_free(struct fuse_backing *fb)
{
	pr_debug("%s: fb=0x%p\n", __func__, fb);

	if (fb->file)
		fput(fb->file);
	put_cred(fb->cred);
	kfree_rcu(fb, rcu);
}

void fuse_backing_put(struct fuse_backing *fb)
{
	if (fb && refcount_dec_and_test(&fb->count))
		fuse_backing_free(fb);
}

void fuse_backing_files_init(struct fuse_conn *fc)
{
	idr_init(&fc->backing_files_map);
}

static int fuse_backing_id_alloc(struct fuse_conn *fc, struct fuse_backing *fb)
{
	int id;

	idr_preload(GFP_KERNEL);
	spin_lock(&fc->lock);
	/* FIXME: xarray might be space inefficient */
	id = idr_alloc_cyclic(&fc->backing_files_map, fb, 1, 0, GFP_ATOMIC);
	spin_unlock(&fc->lock);
	idr_preload_end();

	WARN_ON_ONCE(id == 0);
	return id;
}

static struct fuse_backing *fuse_backing_id_remove(struct fuse_conn *fc,
						   int id)
{
	struct fuse_backing *fb;

	spin_lock(&fc->lock);
	fb = idr_remove(&fc->backing_files_map, id);
	spin_unlock(&fc->lock);

	return fb;
}

static int fuse_backing_id_free(int id, void *p, void *data)
{
	struct fuse_backing *fb = p;

	WARN_ON_ONCE(refcount_read(&fb->count) != 1);
	fuse_backing_free(fb);
	return 0;
}

void fuse_backing_files_free(struct fuse_conn *fc)
{
	idr_for_each(&fc->backing_files_map, fuse_backing_id_free, NULL);
	idr_destroy(&fc->backing_files_map);
}

int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map)
{
	struct file *file;
	struct super_block *backing_sb;
	struct fuse_backing *fb = NULL;
	int res;

	pr_debug("%s: fd=%d flags=0x%x\n", __func__, map->fd, map->flags);

	/* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */
	res = -EPERM;
	if (!fc->passthrough || !capable(CAP_SYS_ADMIN))
		goto out;

	res = -EINVAL;
	if (map->flags)
		goto out;

	file = fget(map->fd);
	res = -EBADF;
	if (!file)
		goto out;

	res = -EOPNOTSUPP;
	if (!file->f_op->read_iter || !file->f_op->write_iter)
		goto out_fput;

	backing_sb = file_inode(file)->i_sb;
	res = -ELOOP;
	if (backing_sb->s_stack_depth >= fc->max_stack_depth)
		goto out_fput;

	fb = kmalloc(sizeof(struct fuse_backing), GFP_KERNEL);
	res = -ENOMEM;
	if (!fb)
		goto out_fput;

	fb->file = file;
	fb->cred = prepare_creds();
	refcount_set(&fb->count, 1);

	res = fuse_backing_id_alloc(fc, fb);
	if (res < 0) {
		fuse_backing_free(fb);
		fb = NULL;
	}

out:
	pr_debug("%s: fb=0x%p, ret=%i\n", __func__, fb, res);

	return res;

out_fput:
	fput(file);
	goto out;
}

int fuse_backing_close(struct fuse_conn *fc, int backing_id)
{
	struct fuse_backing *fb = NULL;
	int err;

	pr_debug("%s: backing_id=%d\n", __func__, backing_id);

	/* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */
	err = -EPERM;
	if (!fc->passthrough || !capable(CAP_SYS_ADMIN))
		goto out;

	err = -EINVAL;
	if (backing_id <= 0)
		goto out;

	err = -ENOENT;
	fb = fuse_backing_id_remove(fc, backing_id);
	if (!fb)
		goto out;

	fuse_backing_put(fb);
	err = 0;
out:
	pr_debug("%s: fb=0x%p, err=%i\n", __func__, fb, err);

	return err;
}

/*
 * Setup passthrough to a backing file.
 *
 * Returns an fb object with elevated refcount to be stored in fuse inode.
 */
struct fuse_backing *fuse_passthrough_open(struct file *file,
					   struct inode *inode,
					   int backing_id)
{
	struct fuse_file *ff = file->private_data;
	struct fuse_conn *fc = ff->fm->fc;
	struct fuse_backing *fb = NULL;
	struct file *backing_file;
	int err;

	err = -EINVAL;
	if (backing_id <= 0)
		goto out;

	rcu_read_lock();
	fb = idr_find(&fc->backing_files_map, backing_id);
	fb = fuse_backing_get(fb);
	rcu_read_unlock();

	err = -ENOENT;
	if (!fb)
		goto out;

	/* Allocate backing file per fuse file to store fuse path */
	backing_file = backing_file_open(&file->f_path, file->f_flags,
					 &fb->file->f_path, fb->cred);
	err = PTR_ERR(backing_file);
	if (IS_ERR(backing_file)) {
		fuse_backing_put(fb);
		goto out;
	}

	err = 0;
	ff->passthrough = backing_file;
	ff->cred = get_cred(fb->cred);
out:
	pr_debug("%s: backing_id=%d, fb=0x%p, backing_file=0x%p, err=%i\n", __func__,
		 backing_id, fb, ff->passthrough, err);

	return err ? ERR_PTR(err) : fb;
}

void fuse_passthrough_release(struct fuse_file *ff, struct fuse_backing *fb)
{
	pr_debug("%s: fb=0x%p, backing_file=0x%p\n", __func__,
		 fb, ff->passthrough);

	fput(ff->passthrough);
	ff->passthrough = NULL;
	put_cred(ff->cred);
	ff->cred = NULL;
}
Commit	Line	Data
7dc4e97a AG	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* FUSE passthrough to backing file.
	4	*
	5	* Copyright (c) 2023 CTERA Networks.
	6	*/
	7
	8	#include "fuse_i.h"
	9
	10	#include <linux/file.h>
4a90451b	11	#include <linux/backing-file.h>
5ca73468	12	#include <linux/splice.h>
7dc4e97a	13
57e1176e AG	14	static void fuse_file_accessed(struct file *file)
	15	{
	16	struct inode *inode = file_inode(file);
	17
	18	fuse_invalidate_atime(inode);
	19	}
	20
	21	static void fuse_file_modified(struct file *file)
	22	{
	23	struct inode *inode = file_inode(file);
	24
	25	fuse_invalidate_attr_mask(inode, FUSE_STATX_MODSIZE);
	26	}
	27
	28	ssize_t fuse_passthrough_read_iter(struct kiocb iocb, struct iov_iter iter)
	29	{
	30	struct file *file = iocb->ki_filp;
	31	struct fuse_file *ff = file->private_data;
	32	struct file *backing_file = fuse_file_passthrough(ff);
	33	size_t count = iov_iter_count(iter);
	34	ssize_t ret;
	35	struct backing_file_ctx ctx = {
	36	.cred = ff->cred,
	37	.user_file = file,
	38	.accessed = fuse_file_accessed,
	39	};
	40
	41
	42	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu\n", __func__,
	43	backing_file, iocb->ki_pos, count);
	44
	45	if (!count)
	46	return 0;
	47
	48	ret = backing_file_read_iter(backing_file, iter, iocb, iocb->ki_flags,
	49	&ctx);
	50
	51	return ret;
	52	}
	53
	54	ssize_t fuse_passthrough_write_iter(struct kiocb *iocb,
	55	struct iov_iter *iter)
	56	{
	57	struct file *file = iocb->ki_filp;
	58	struct inode *inode = file_inode(file);
	59	struct fuse_file *ff = file->private_data;
	60	struct file *backing_file = fuse_file_passthrough(ff);
	61	size_t count = iov_iter_count(iter);
	62	ssize_t ret;
	63	struct backing_file_ctx ctx = {
	64	.cred = ff->cred,
	65	.user_file = file,
	66	.end_write = fuse_file_modified,
	67	};
	68
	69	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu\n", __func__,
	70	backing_file, iocb->ki_pos, count);
	71
	72	if (!count)
	73	return 0;
	74
	75	inode_lock(inode);
	76	ret = backing_file_write_iter(backing_file, iter, iocb, iocb->ki_flags,
	77	&ctx);
78	inode_unlock(inode);
79
80	return ret;
81	}
82
5ca73468 AG	83	ssize_t fuse_passthrough_splice_read(struct file in, loff_t ppos,
	84	struct pipe_inode_info *pipe,
	85	size_t len, unsigned int flags)
	86	{
	87	struct fuse_file *ff = in->private_data;
	88	struct file *backing_file = fuse_file_passthrough(ff);
	89	struct backing_file_ctx ctx = {
	90	.cred = ff->cred,
	91	.user_file = in,
	92	.accessed = fuse_file_accessed,
	93	};
	94
	95	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
	96	backing_file, ppos ? *ppos : 0, len, flags);
	97
	98	return backing_file_splice_read(backing_file, ppos, pipe, len, flags,
	99	&ctx);
	100	}
	101
	102	ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
	103	struct file out, loff_t ppos,
	104	size_t len, unsigned int flags)
	105	{
	106	struct fuse_file *ff = out->private_data;
	107	struct file *backing_file = fuse_file_passthrough(ff);
	108	struct inode *inode = file_inode(out);
	109	ssize_t ret;
	110	struct backing_file_ctx ctx = {
	111	.cred = ff->cred,
	112	.user_file = out,
	113	.end_write = fuse_file_modified,
	114	};
	115
	116	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
	117	backing_file, ppos ? *ppos : 0, len, flags);
	118
	119	inode_lock(inode);
	120	ret = backing_file_splice_write(pipe, backing_file, ppos, len, flags,
	121	&ctx);
	122	inode_unlock(inode);
	123
	124	return ret;
	125	}
	126
7dc4e97a AG	127	struct fuse_backing fuse_backing_get(struct fuse_backing fb)
	128	{
	129	if (fb && refcount_inc_not_zero(&fb->count))
	130	return fb;
	131	return NULL;
	132	}
	133
	134	static void fuse_backing_free(struct fuse_backing *fb)
	135	{
44350256 AG	136	pr_debug("%s: fb=0x%p\n", __func__, fb);
44350256 AG	137
7dc4e97a AG	138	if (fb->file)
7dc4e97a AG	139	fput(fb->file);
44350256	140	put_cred(fb->cred);
7dc4e97a AG	141	kfree_rcu(fb, rcu);
	142	}
	143
	144	void fuse_backing_put(struct fuse_backing *fb)
	145	{
	146	if (fb && refcount_dec_and_test(&fb->count))
	147	fuse_backing_free(fb);
	148	}
44350256 AG	149
	150	void fuse_backing_files_init(struct fuse_conn *fc)
	151	{
	152	idr_init(&fc->backing_files_map);
	153	}
	154
	155	static int fuse_backing_id_alloc(struct fuse_conn fc, struct fuse_backing fb)
	156	{
	157	int id;
	158
	159	idr_preload(GFP_KERNEL);
	160	spin_lock(&fc->lock);
	161	/* FIXME: xarray might be space inefficient */
	162	id = idr_alloc_cyclic(&fc->backing_files_map, fb, 1, 0, GFP_ATOMIC);
	163	spin_unlock(&fc->lock);
	164	idr_preload_end();
	165
	166	WARN_ON_ONCE(id == 0);
	167	return id;
	168	}
	169
	170	static struct fuse_backing fuse_backing_id_remove(struct fuse_conn fc,
	171	int id)
	172	{
	173	struct fuse_backing *fb;
	174
	175	spin_lock(&fc->lock);
	176	fb = idr_remove(&fc->backing_files_map, id);
	177	spin_unlock(&fc->lock);
	178
	179	return fb;
	180	}
	181
	182	static int fuse_backing_id_free(int id, void p, void data)
	183	{
	184	struct fuse_backing *fb = p;
	185
	186	WARN_ON_ONCE(refcount_read(&fb->count) != 1);
	187	fuse_backing_free(fb);
	188	return 0;
	189	}
	190
	191	void fuse_backing_files_free(struct fuse_conn *fc)
	192	{
	193	idr_for_each(&fc->backing_files_map, fuse_backing_id_free, NULL);
	194	idr_destroy(&fc->backing_files_map);
	195	}
	196
	197	int fuse_backing_open(struct fuse_conn fc, struct fuse_backing_map map)
	198	{
	199	struct file *file;
	200	struct super_block *backing_sb;
	201	struct fuse_backing *fb = NULL;
	202	int res;
	203
	204	pr_debug("%s: fd=%d flags=0x%x\n", __func__, map->fd, map->flags);
	205
	206	/* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */
	207	res = -EPERM;
	208	if (!fc->passthrough \|\| !capable(CAP_SYS_ADMIN))
	209	goto out;
	210
	211	res = -EINVAL;
	212	if (map->flags)
213	goto out;
214
215	file = fget(map->fd);
216	res = -EBADF;
217	if (!file)
218	goto out;
219
220	res = -EOPNOTSUPP;
221	if (!file->f_op->read_iter \|\| !file->f_op->write_iter)
222	goto out_fput;
223
224	backing_sb = file_inode(file)->i_sb;
225	res = -ELOOP;
226	if (backing_sb->s_stack_depth >= fc->max_stack_depth)
227	goto out_fput;
228
229	fb = kmalloc(sizeof(struct fuse_backing), GFP_KERNEL);
230	res = -ENOMEM;
231	if (!fb)
232	goto out_fput;
233
234	fb->file = file;
235	fb->cred = prepare_creds();
236	refcount_set(&fb->count, 1);
237
238	res = fuse_backing_id_alloc(fc, fb);
239	if (res < 0) {
240	fuse_backing_free(fb);
241	fb = NULL;
242	}
243
244	out:
245	pr_debug("%s: fb=0x%p, ret=%i\n", __func__, fb, res);
246
247	return res;
248
249	out_fput:
250	fput(file);
251	goto out;
252	}
253
254	int fuse_backing_close(struct fuse_conn *fc, int backing_id)
255	{
256	struct fuse_backing *fb = NULL;
257	int err;
258
259	pr_debug("%s: backing_id=%d\n", __func__, backing_id);
260
261	/* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */
262	err = -EPERM;
263	if (!fc->passthrough \|\| !capable(CAP_SYS_ADMIN))
264	goto out;
265
266	err = -EINVAL;
267	if (backing_id <= 0)
268	goto out;
269
270	err = -ENOENT;
271	fb = fuse_backing_id_remove(fc, backing_id);
272	if (!fb)
273	goto out;
274
275	fuse_backing_put(fb);
276	err = 0;
277	out:
278	pr_debug("%s: fb=0x%p, err=%i\n", __func__, fb, err);
279
280	return err;
281	}
4a90451b AG	282
	283	/*
	284	* Setup passthrough to a backing file.
	285	*
	286	* Returns an fb object with elevated refcount to be stored in fuse inode.
	287	*/
	288	struct fuse_backing fuse_passthrough_open(struct file file,
	289	struct inode *inode,
	290	int backing_id)
	291	{
	292	struct fuse_file *ff = file->private_data;
	293	struct fuse_conn *fc = ff->fm->fc;
	294	struct fuse_backing *fb = NULL;
	295	struct file *backing_file;
	296	int err;
	297
	298	err = -EINVAL;
	299	if (backing_id <= 0)
	300	goto out;
	301
	302	rcu_read_lock();
	303	fb = idr_find(&fc->backing_files_map, backing_id);
	304	fb = fuse_backing_get(fb);
	305	rcu_read_unlock();
	306
	307	err = -ENOENT;
	308	if (!fb)
	309	goto out;
	310
	311	/* Allocate backing file per fuse file to store fuse path */
	312	backing_file = backing_file_open(&file->f_path, file->f_flags,
	313	&fb->file->f_path, fb->cred);
	314	err = PTR_ERR(backing_file);
	315	if (IS_ERR(backing_file)) {
	316	fuse_backing_put(fb);
	317	goto out;
	318	}
	319
	320	err = 0;
	321	ff->passthrough = backing_file;
	322	ff->cred = get_cred(fb->cred);
	323	out:
	324	pr_debug("%s: backing_id=%d, fb=0x%p, backing_file=0x%p, err=%i\n", __func__,
	325	backing_id, fb, ff->passthrough, err);
	326
	327	return err ? ERR_PTR(err) : fb;
	328	}
	329
	330	void fuse_passthrough_release(struct fuse_file ff, struct fuse_backing fb)
	331	{
	332	pr_debug("%s: fb=0x%p, backing_file=0x%p\n", __func__,
	333	fb, ff->passthrough);
	334
	335	fput(ff->passthrough);
	336	ff->passthrough = NULL;
	337	put_cred(ff->cred);
	338	ff->cred = NULL;
	339	}