[linux-2.6-block.git] / fs / f2fs / verity.c

// SPDX-License-Identifier: GPL-2.0
/*
 * fs/f2fs/verity.c: fs-verity support for f2fs
 *
 * Copyright 2019 Google LLC
 */

/*
 * Implementation of fsverity_operations for f2fs.
 *
 * Like ext4, f2fs stores the verity metadata (Merkle tree and
 * fsverity_descriptor) past the end of the file, starting at the first 64K
 * boundary beyond i_size.  This approach works because (a) verity files are
 * readonly, and (b) pages fully beyond i_size aren't visible to userspace but
 * can be read/written internally by f2fs with only some relatively small
 * changes to f2fs.  Extended attributes cannot be used because (a) f2fs limits
 * the total size of an inode's xattr entries to 4096 bytes, which wouldn't be
 * enough for even a single Merkle tree block, and (b) f2fs encryption doesn't
 * encrypt xattrs, yet the verity metadata *must* be encrypted when the file is
 * because it contains hashes of the plaintext data.
 *
 * Using a 64K boundary rather than a 4K one keeps things ready for
 * architectures with 64K pages, and it doesn't necessarily waste space on-disk
 * since there can be a hole between i_size and the start of the Merkle tree.
 */

#include <linux/f2fs_fs.h>

#include "f2fs.h"
#include "xattr.h"

static inline loff_t f2fs_verity_metadata_pos(const struct inode *inode)
{
	return round_up(inode->i_size, 65536);
}

/*
 * Read some verity metadata from the inode.  __vfs_read() can't be used because
 * we need to read beyond i_size.
 */
static int pagecache_read(struct inode *inode, void *buf, size_t count,
			  loff_t pos)
{
	while (count) {
		size_t n = min_t(size_t, count,
				 PAGE_SIZE - offset_in_page(pos));
		struct page *page;
		void *addr;

		page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
					 NULL);
		if (IS_ERR(page))
			return PTR_ERR(page);

		addr = kmap_atomic(page);
		memcpy(buf, addr + offset_in_page(pos), n);
		kunmap_atomic(addr);

		put_page(page);

		buf += n;
		pos += n;
		count -= n;
	}
	return 0;
}

/*
 * Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
 * kernel_write() can't be used because the file descriptor is readonly.
 */
static int pagecache_write(struct inode *inode, const void *buf, size_t count,
			   loff_t pos)
{
	if (pos + count > inode->i_sb->s_maxbytes)
		return -EFBIG;

	while (count) {
		size_t n = min_t(size_t, count,
				 PAGE_SIZE - offset_in_page(pos));
		struct page *page;
		void *fsdata;
		void *addr;
		int res;

		res = pagecache_write_begin(NULL, inode->i_mapping, pos, n, 0,
					    &page, &fsdata);
		if (res)
			return res;

		addr = kmap_atomic(page);
		memcpy(addr + offset_in_page(pos), buf, n);
		kunmap_atomic(addr);

		res = pagecache_write_end(NULL, inode->i_mapping, pos, n, n,
					  page, fsdata);
		if (res < 0)
			return res;
		if (res != n)
			return -EIO;

		buf += n;
		pos += n;
		count -= n;
	}
	return 0;
}

/*
 * Format of f2fs verity xattr.  This points to the location of the verity
 * descriptor within the file data rather than containing it directly because
 * the verity descriptor *must* be encrypted when f2fs encryption is used.  But,
 * f2fs encryption does not encrypt xattrs.
 */
struct fsverity_descriptor_location {
	__le32 version;
	__le32 size;
	__le64 pos;
};

static int f2fs_begin_enable_verity(struct file *filp)
{
	struct inode *inode = file_inode(filp);
	int err;

	if (f2fs_verity_in_progress(inode))
		return -EBUSY;

	if (f2fs_is_atomic_file(inode) || f2fs_is_volatile_file(inode))
		return -EOPNOTSUPP;

	/*
	 * Since the file was opened readonly, we have to initialize the quotas
	 * here and not rely on ->open() doing it.  This must be done before
	 * evicting the inline data.
	 */
	err = dquot_initialize(inode);
	if (err)
		return err;

	err = f2fs_convert_inline_inode(inode);
	if (err)
		return err;

	set_inode_flag(inode, FI_VERITY_IN_PROGRESS);
	return 0;
}

static int f2fs_end_enable_verity(struct file *filp, const void *desc,
				  size_t desc_size, u64 merkle_tree_size)
{
	struct inode *inode = file_inode(filp);
	u64 desc_pos = f2fs_verity_metadata_pos(inode) + merkle_tree_size;
	struct fsverity_descriptor_location dloc = {
		.version = cpu_to_le32(1),
		.size = cpu_to_le32(desc_size),
		.pos = cpu_to_le64(desc_pos),
	};
	int err = 0;

	if (desc != NULL) {
		/* Succeeded; write the verity descriptor. */
		err = pagecache_write(inode, desc, desc_size, desc_pos);

		/* Write all pages before clearing FI_VERITY_IN_PROGRESS. */
		if (!err)
			err = filemap_write_and_wait(inode->i_mapping);
	}

	/* If we failed, truncate anything we wrote past i_size. */
	if (desc == NULL || err)
		f2fs_truncate(inode);

	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);

	if (desc != NULL && !err) {
		err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
				    F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
				    NULL, XATTR_CREATE);
		if (!err) {
			file_set_verity(inode);
			f2fs_set_inode_flags(inode);
			f2fs_mark_inode_dirty_sync(inode, true);
		}
	}
	return err;
}

static int f2fs_get_verity_descriptor(struct inode *inode, void *buf,
				      size_t buf_size)
{
	struct fsverity_descriptor_location dloc;
	int res;
	u32 size;
	u64 pos;

	/* Get the descriptor location */
	res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_VERITY,
			    F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc), NULL);
	if (res < 0 && res != -ERANGE)
		return res;
	if (res != sizeof(dloc) || dloc.version != cpu_to_le32(1)) {
		f2fs_warn(F2FS_I_SB(inode), "unknown verity xattr format");
		return -EINVAL;
	}
	size = le32_to_cpu(dloc.size);
	pos = le64_to_cpu(dloc.pos);

	/* Get the descriptor */
	if (pos + size < pos || pos + size > inode->i_sb->s_maxbytes ||
	    pos < f2fs_verity_metadata_pos(inode) || size > INT_MAX) {
		f2fs_warn(F2FS_I_SB(inode), "invalid verity xattr");
		return -EFSCORRUPTED;
	}
	if (buf_size) {
		if (size > buf_size)
			return -ERANGE;
		res = pagecache_read(inode, buf, size, pos);
		if (res)
			return res;
	}
	return size;
}

/*
 * Prefetch some pages from the file's Merkle tree.
 *
 * This is basically a stripped-down version of __do_page_cache_readahead()
 * which works on pages past i_size.
 */
static void f2fs_merkle_tree_readahead(struct address_space *mapping,
				       pgoff_t start_index, unsigned long count)
{
	LIST_HEAD(pages);
	unsigned int nr_pages = 0;
	struct page *page;
	pgoff_t index;
	struct blk_plug plug;

	for (index = start_index; index < start_index + count; index++) {
		page = xa_load(&mapping->i_pages, index);
		if (!page || xa_is_value(page)) {
			page = __page_cache_alloc(readahead_gfp_mask(mapping));
			if (!page)
				break;
			page->index = index;
			list_add(&page->lru, &pages);
			nr_pages++;
		}
	}
	blk_start_plug(&plug);
	f2fs_mpage_readpages(mapping, &pages, NULL, nr_pages, true);
	blk_finish_plug(&plug);
}

static struct page *f2fs_read_merkle_tree_page(struct inode *inode,
					       pgoff_t index,
					       unsigned long num_ra_pages)
{
	struct page *page;

	index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT;

	page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED);
	if (!page || !PageUptodate(page)) {
		if (page)
			put_page(page);
		else if (num_ra_pages > 1)
			f2fs_merkle_tree_readahead(inode->i_mapping, index,
						   num_ra_pages);
		page = read_mapping_page(inode->i_mapping, index, NULL);
	}
	return page;
}

static int f2fs_write_merkle_tree_block(struct inode *inode, const void *buf,
					u64 index, int log_blocksize)
{
	loff_t pos = f2fs_verity_metadata_pos(inode) + (index << log_blocksize);

	return pagecache_write(inode, buf, 1 << log_blocksize, pos);
}

const struct fsverity_operations f2fs_verityops = {
	.begin_enable_verity	= f2fs_begin_enable_verity,
	.end_enable_verity	= f2fs_end_enable_verity,
	.get_verity_descriptor	= f2fs_get_verity_descriptor,
	.read_merkle_tree_page	= f2fs_read_merkle_tree_page,
	.write_merkle_tree_block = f2fs_write_merkle_tree_block,
};
Commit	Line	Data
95ae251f EB	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* fs/f2fs/verity.c: fs-verity support for f2fs
	4	*
	5	* Copyright 2019 Google LLC
	6	*/
	7
	8	/*
	9	* Implementation of fsverity_operations for f2fs.
	10	*
	11	* Like ext4, f2fs stores the verity metadata (Merkle tree and
	12	* fsverity_descriptor) past the end of the file, starting at the first 64K
	13	* boundary beyond i_size. This approach works because (a) verity files are
	14	* readonly, and (b) pages fully beyond i_size aren't visible to userspace but
	15	* can be read/written internally by f2fs with only some relatively small
	16	* changes to f2fs. Extended attributes cannot be used because (a) f2fs limits
	17	* the total size of an inode's xattr entries to 4096 bytes, which wouldn't be
	18	* enough for even a single Merkle tree block, and (b) f2fs encryption doesn't
	19	* encrypt xattrs, yet the verity metadata must be encrypted when the file is
	20	* because it contains hashes of the plaintext data.
	21	*
	22	* Using a 64K boundary rather than a 4K one keeps things ready for
	23	* architectures with 64K pages, and it doesn't necessarily waste space on-disk
	24	* since there can be a hole between i_size and the start of the Merkle tree.
	25	*/
	26
	27	#include <linux/f2fs_fs.h>
	28
	29	#include "f2fs.h"
	30	#include "xattr.h"
	31
	32	static inline loff_t f2fs_verity_metadata_pos(const struct inode *inode)
	33	{
	34	return round_up(inode->i_size, 65536);
	35	}
	36
	37	/*
	38	* Read some verity metadata from the inode. __vfs_read() can't be used because
	39	* we need to read beyond i_size.
	40	*/
	41	static int pagecache_read(struct inode inode, void buf, size_t count,
	42	loff_t pos)
	43	{
	44	while (count) {
	45	size_t n = min_t(size_t, count,
	46	PAGE_SIZE - offset_in_page(pos));
	47	struct page *page;
	48	void *addr;
	49
	50	page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
	51	NULL);
	52	if (IS_ERR(page))
	53	return PTR_ERR(page);
	54
	55	addr = kmap_atomic(page);
	56	memcpy(buf, addr + offset_in_page(pos), n);
	57	kunmap_atomic(addr);
	58
	59	put_page(page);
	60
	61	buf += n;
	62	pos += n;
	63	count -= n;
	64	}
65	return 0;
66	}
67
68	/*
69	* Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
70	* kernel_write() can't be used because the file descriptor is readonly.
71	*/
72	static int pagecache_write(struct inode inode, const void buf, size_t count,
73	loff_t pos)
74	{
75	if (pos + count > inode->i_sb->s_maxbytes)
76	return -EFBIG;
77
78	while (count) {
79	size_t n = min_t(size_t, count,
80	PAGE_SIZE - offset_in_page(pos));
81	struct page *page;
82	void *fsdata;
83	void *addr;
84	int res;
85
86	res = pagecache_write_begin(NULL, inode->i_mapping, pos, n, 0,
87	&page, &fsdata);
88	if (res)
89	return res;
90
91	addr = kmap_atomic(page);
92	memcpy(addr + offset_in_page(pos), buf, n);
93	kunmap_atomic(addr);
94
95	res = pagecache_write_end(NULL, inode->i_mapping, pos, n, n,
96	page, fsdata);
97	if (res < 0)
98	return res;
99	if (res != n)
100	return -EIO;
101
102	buf += n;
103	pos += n;
104	count -= n;
105	}
106	return 0;
107	}
108
109	/*
110	* Format of f2fs verity xattr. This points to the location of the verity
111	* descriptor within the file data rather than containing it directly because
112	* the verity descriptor must be encrypted when f2fs encryption is used. But,
113	* f2fs encryption does not encrypt xattrs.
114	*/
115	struct fsverity_descriptor_location {
116	__le32 version;
117	__le32 size;
118	__le64 pos;
119	};
120
121	static int f2fs_begin_enable_verity(struct file *filp)
122	{
123	struct inode *inode = file_inode(filp);
124	int err;
125
126	if (f2fs_verity_in_progress(inode))
127	return -EBUSY;
128
129	if (f2fs_is_atomic_file(inode) \|\| f2fs_is_volatile_file(inode))
130	return -EOPNOTSUPP;
131
132	/*
133	* Since the file was opened readonly, we have to initialize the quotas
134	* here and not rely on ->open() doing it. This must be done before
135	* evicting the inline data.
136	*/
137	err = dquot_initialize(inode);
138	if (err)
139	return err;
140
141	err = f2fs_convert_inline_inode(inode);
142	if (err)
143	return err;
144
145	set_inode_flag(inode, FI_VERITY_IN_PROGRESS);
146	return 0;
147	}
148
149	static int f2fs_end_enable_verity(struct file filp, const void desc,
150	size_t desc_size, u64 merkle_tree_size)
151	{
152	struct inode *inode = file_inode(filp);
153	u64 desc_pos = f2fs_verity_metadata_pos(inode) + merkle_tree_size;
154	struct fsverity_descriptor_location dloc = {
155	.version = cpu_to_le32(1),
156	.size = cpu_to_le32(desc_size),
157	.pos = cpu_to_le64(desc_pos),
158	};
159	int err = 0;
160
161	if (desc != NULL) {
162	/* Succeeded; write the verity descriptor. */
163	err = pagecache_write(inode, desc, desc_size, desc_pos);
164
165	/* Write all pages before clearing FI_VERITY_IN_PROGRESS. */
166	if (!err)
167	err = filemap_write_and_wait(inode->i_mapping);
168	}
169
170	/* If we failed, truncate anything we wrote past i_size. */
171	if (desc == NULL \|\| err)
172	f2fs_truncate(inode);
173
174	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
175
176	if (desc != NULL && !err) {
177	err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
178	F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
179	NULL, XATTR_CREATE);
180	if (!err) {
181	file_set_verity(inode);
182	f2fs_set_inode_flags(inode);
183	f2fs_mark_inode_dirty_sync(inode, true);
184	}
185	}
186	return err;
187	}
188
189	static int f2fs_get_verity_descriptor(struct inode inode, void buf,
190	size_t buf_size)
191	{
192	struct fsverity_descriptor_location dloc;
193	int res;
194	u32 size;
195	u64 pos;
196
197	/* Get the descriptor location */
198	res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_VERITY,
199	F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc), NULL);
200	if (res < 0 && res != -ERANGE)
201	return res;
202	if (res != sizeof(dloc) \|\| dloc.version != cpu_to_le32(1)) {
203	f2fs_warn(F2FS_I_SB(inode), "unknown verity xattr format");
204	return -EINVAL;
205	}
206	size = le32_to_cpu(dloc.size);
207	pos = le64_to_cpu(dloc.pos);
208
209	/* Get the descriptor */
210	if (pos + size < pos \|\| pos + size > inode->i_sb->s_maxbytes \|\|
211	pos < f2fs_verity_metadata_pos(inode) \|\| size > INT_MAX) {
212	f2fs_warn(F2FS_I_SB(inode), "invalid verity xattr");
213	return -EFSCORRUPTED;
214	}
215	if (buf_size) {
216	if (size > buf_size)
217	return -ERANGE;
218	res = pagecache_read(inode, buf, size, pos);
219	if (res)
220	return res;
221	}
222	return size;
223	}
224
fd39073d EB	225	/*
	226	* Prefetch some pages from the file's Merkle tree.
	227	*
	228	* This is basically a stripped-down version of __do_page_cache_readahead()
	229	* which works on pages past i_size.
	230	*/
	231	static void f2fs_merkle_tree_readahead(struct address_space *mapping,
	232	pgoff_t start_index, unsigned long count)
	233	{
	234	LIST_HEAD(pages);
	235	unsigned int nr_pages = 0;
	236	struct page *page;
	237	pgoff_t index;
	238	struct blk_plug plug;
	239
	240	for (index = start_index; index < start_index + count; index++) {
	241	page = xa_load(&mapping->i_pages, index);
	242	if (!page \|\| xa_is_value(page)) {
	243	page = __page_cache_alloc(readahead_gfp_mask(mapping));
	244	if (!page)
	245	break;
	246	page->index = index;
	247	list_add(&page->lru, &pages);
	248	nr_pages++;
	249	}
	250	}
	251	blk_start_plug(&plug);
	252	f2fs_mpage_readpages(mapping, &pages, NULL, nr_pages, true);
	253	blk_finish_plug(&plug);
	254	}
	255
95ae251f	256	static struct page f2fs_read_merkle_tree_page(struct inode inode,
fd39073d EB	257	pgoff_t index,
fd39073d EB	258	unsigned long num_ra_pages)
95ae251f	259	{
fd39073d EB	260	struct page *page;
fd39073d EB	261
95ae251f EB	262	index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT;
95ae251f EB	263
fd39073d EB	264	page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED);
	265	if (!page \|\| !PageUptodate(page)) {
	266	if (page)
	267	put_page(page);
	268	else if (num_ra_pages > 1)
	269	f2fs_merkle_tree_readahead(inode->i_mapping, index,
	270	num_ra_pages);
	271	page = read_mapping_page(inode->i_mapping, index, NULL);
	272	}
	273	return page;
95ae251f EB	274	}
	275
	276	static int f2fs_write_merkle_tree_block(struct inode inode, const void buf,
	277	u64 index, int log_blocksize)
	278	{
	279	loff_t pos = f2fs_verity_metadata_pos(inode) + (index << log_blocksize);
	280
	281	return pagecache_write(inode, buf, 1 << log_blocksize, pos);
	282	}
	283
	284	const struct fsverity_operations f2fs_verityops = {
	285	.begin_enable_verity = f2fs_begin_enable_verity,
	286	.end_enable_verity = f2fs_end_enable_verity,
	287	.get_verity_descriptor = f2fs_get_verity_descriptor,
	288	.read_merkle_tree_page = f2fs_read_merkle_tree_page,
	289	.write_merkle_tree_block = f2fs_write_merkle_tree_block,
	290	};