[mirror_ubuntu-hirsute-kernel.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"

#define F2FS_VERIFY_VER	(1)

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(F2FS_VERIFY_VER),
		.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(F2FS_VERIFY_VER)) {
		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;
}

static struct page *f2fs_read_merkle_tree_page(struct inode *inode,
					       pgoff_t index,
					       unsigned long num_ra_pages)
{
	DEFINE_READAHEAD(ractl, NULL, inode->i_mapping, index);
	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)
			page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
		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
8fa41016 JQ	32	#define F2FS_VERIFY_VER (1)
8fa41016 JQ	33
95ae251f EB	34	static inline loff_t f2fs_verity_metadata_pos(const struct inode *inode)
	35	{
	36	return round_up(inode->i_size, 65536);
	37	}
	38
	39	/*
	40	* Read some verity metadata from the inode. __vfs_read() can't be used because
	41	* we need to read beyond i_size.
	42	*/
	43	static int pagecache_read(struct inode inode, void buf, size_t count,
	44	loff_t pos)
	45	{
	46	while (count) {
	47	size_t n = min_t(size_t, count,
	48	PAGE_SIZE - offset_in_page(pos));
	49	struct page *page;
	50	void *addr;
	51
	52	page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
	53	NULL);
	54	if (IS_ERR(page))
	55	return PTR_ERR(page);
	56
	57	addr = kmap_atomic(page);
	58	memcpy(buf, addr + offset_in_page(pos), n);
	59	kunmap_atomic(addr);
	60
	61	put_page(page);
	62
	63	buf += n;
	64	pos += n;
	65	count -= n;
	66	}
	67	return 0;
	68	}
	69
	70	/*
	71	* Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
	72	* kernel_write() can't be used because the file descriptor is readonly.
	73	*/
	74	static int pagecache_write(struct inode inode, const void buf, size_t count,
	75	loff_t pos)
	76	{
	77	if (pos + count > inode->i_sb->s_maxbytes)
	78	return -EFBIG;
	79
	80	while (count) {
	81	size_t n = min_t(size_t, count,
	82	PAGE_SIZE - offset_in_page(pos));
	83	struct page *page;
	84	void *fsdata;
	85	void *addr;
	86	int res;
	87
	88	res = pagecache_write_begin(NULL, inode->i_mapping, pos, n, 0,
	89	&page, &fsdata);
	90	if (res)
	91	return res;
	92
	93	addr = kmap_atomic(page);
	94	memcpy(addr + offset_in_page(pos), buf, n);
	95	kunmap_atomic(addr);
	96
	97	res = pagecache_write_end(NULL, inode->i_mapping, pos, n, n,
98	page, fsdata);
99	if (res < 0)
100	return res;
101	if (res != n)
102	return -EIO;
103
104	buf += n;
105	pos += n;
106	count -= n;
107	}
108	return 0;
109	}
110
111	/*
112	* Format of f2fs verity xattr. This points to the location of the verity
113	* descriptor within the file data rather than containing it directly because
114	* the verity descriptor must be encrypted when f2fs encryption is used. But,
115	* f2fs encryption does not encrypt xattrs.
116	*/
117	struct fsverity_descriptor_location {
118	__le32 version;
119	__le32 size;
120	__le64 pos;
121	};
122
123	static int f2fs_begin_enable_verity(struct file *filp)
124	{
125	struct inode *inode = file_inode(filp);
126	int err;
127
128	if (f2fs_verity_in_progress(inode))
129	return -EBUSY;
130
131	if (f2fs_is_atomic_file(inode) \|\| f2fs_is_volatile_file(inode))
132	return -EOPNOTSUPP;
133
134	/*
135	* Since the file was opened readonly, we have to initialize the quotas
136	* here and not rely on ->open() doing it. This must be done before
137	* evicting the inline data.
138	*/
139	err = dquot_initialize(inode);
140	if (err)
141	return err;
142
143	err = f2fs_convert_inline_inode(inode);
144	if (err)
145	return err;
146
147	set_inode_flag(inode, FI_VERITY_IN_PROGRESS);
148	return 0;
149	}
150
151	static int f2fs_end_enable_verity(struct file filp, const void desc,
152	size_t desc_size, u64 merkle_tree_size)
153	{
154	struct inode *inode = file_inode(filp);
155	u64 desc_pos = f2fs_verity_metadata_pos(inode) + merkle_tree_size;
156	struct fsverity_descriptor_location dloc = {
8fa41016	157	.version = cpu_to_le32(F2FS_VERIFY_VER),
95ae251f EB	158	.size = cpu_to_le32(desc_size),
	159	.pos = cpu_to_le64(desc_pos),
	160	};
	161	int err = 0;
	162
	163	if (desc != NULL) {
	164	/* Succeeded; write the verity descriptor. */
	165	err = pagecache_write(inode, desc, desc_size, desc_pos);
	166
	167	/* Write all pages before clearing FI_VERITY_IN_PROGRESS. */
	168	if (!err)
	169	err = filemap_write_and_wait(inode->i_mapping);
	170	}
	171
	172	/* If we failed, truncate anything we wrote past i_size. */
	173	if (desc == NULL \|\| err)
	174	f2fs_truncate(inode);
	175
	176	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
	177
	178	if (desc != NULL && !err) {
	179	err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
	180	F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
	181	NULL, XATTR_CREATE);
	182	if (!err) {
	183	file_set_verity(inode);
	184	f2fs_set_inode_flags(inode);
	185	f2fs_mark_inode_dirty_sync(inode, true);
	186	}
	187	}
	188	return err;
	189	}
	190
	191	static int f2fs_get_verity_descriptor(struct inode inode, void buf,
	192	size_t buf_size)
	193	{
	194	struct fsverity_descriptor_location dloc;
	195	int res;
	196	u32 size;
	197	u64 pos;
	198
	199	/* Get the descriptor location */
	200	res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_VERITY,
	201	F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc), NULL);
	202	if (res < 0 && res != -ERANGE)
	203	return res;
8fa41016	204	if (res != sizeof(dloc) \|\| dloc.version != cpu_to_le32(F2FS_VERIFY_VER)) {
95ae251f EB	205	f2fs_warn(F2FS_I_SB(inode), "unknown verity xattr format");
	206	return -EINVAL;
	207	}
	208	size = le32_to_cpu(dloc.size);
	209	pos = le64_to_cpu(dloc.pos);
	210
	211	/* Get the descriptor */
	212	if (pos + size < pos \|\| pos + size > inode->i_sb->s_maxbytes \|\|
	213	pos < f2fs_verity_metadata_pos(inode) \|\| size > INT_MAX) {
	214	f2fs_warn(F2FS_I_SB(inode), "invalid verity xattr");
	215	return -EFSCORRUPTED;
	216	}
	217	if (buf_size) {
	218	if (size > buf_size)
	219	return -ERANGE;
	220	res = pagecache_read(inode, buf, size, pos);
	221	if (res)
	222	return res;
	223	}
	224	return size;
	225	}
	226
	227	static struct page f2fs_read_merkle_tree_page(struct inode inode,
fd39073d EB	228	pgoff_t index,
fd39073d EB	229	unsigned long num_ra_pages)
95ae251f	230	{
73bb49da	231	DEFINE_READAHEAD(ractl, NULL, inode->i_mapping, index);
fd39073d EB	232	struct page *page;
fd39073d EB	233
95ae251f EB	234	index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT;
95ae251f EB	235
fd39073d EB	236	page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED);
	237	if (!page \|\| !PageUptodate(page)) {
	238	if (page)
	239	put_page(page);
	240	else if (num_ra_pages > 1)
73bb49da	241	page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
fd39073d EB	242	page = read_mapping_page(inode->i_mapping, index, NULL);
	243	}
	244	return page;
95ae251f EB	245	}
	246
	247	static int f2fs_write_merkle_tree_block(struct inode inode, const void buf,
	248	u64 index, int log_blocksize)
	249	{
	250	loff_t pos = f2fs_verity_metadata_pos(inode) + (index << log_blocksize);
	251
	252	return pagecache_write(inode, buf, 1 << log_blocksize, pos);
	253	}
	254
	255	const struct fsverity_operations f2fs_verityops = {
	256	.begin_enable_verity = f2fs_begin_enable_verity,
	257	.end_enable_verity = f2fs_end_enable_verity,
	258	.get_verity_descriptor = f2fs_get_verity_descriptor,
	259	.read_merkle_tree_page = f2fs_read_merkle_tree_page,
	260	.write_merkle_tree_block = f2fs_write_merkle_tree_block,
	261	};