fs/f2fs/verity.c - linux - Git at Google

 // 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)
 {
 	struct address_space *mapping = inode->i_mapping;
 	const struct address_space_operations *aops = mapping->a_ops;

 	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 = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
 		if (res)
 			return res;

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

 		res = aops->write_end(NULL, 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))
 		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 = f2fs_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);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	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, err2 = 0;

 	/*
 	 * If an error already occurred (which fs/verity/ signals by passing
 	 * desc == NULL), then only clean-up is needed.
 	 */
 	if (desc == NULL)
 		goto cleanup;

 	/* Append the verity descriptor. */
 	err = pagecache_write(inode, desc, desc_size, desc_pos);
 	if (err)
 		goto cleanup;

 	/*
 	 * Write all pages (both data and verity metadata).  Note that this must
 	 * happen before clearing FI_VERITY_IN_PROGRESS; otherwise pages beyond
 	 * i_size won't be written properly.  For crash consistency, this also
 	 * must happen before the verity inode flag gets persisted.
 	 */
 	err = filemap_write_and_wait(inode->i_mapping);
 	if (err)
 		goto cleanup;

 	/* Set the verity xattr. */
 	err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
 			    F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
 			    NULL, XATTR_CREATE);
 	if (err)
 		goto cleanup;

 	/* Finally, set the verity inode flag. */
 	file_set_verity(inode);
 	f2fs_set_inode_flags(inode);
 	f2fs_mark_inode_dirty_sync(inode, true);

 	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
 	return 0;

 cleanup:
 	/*
 	 * Verity failed to be enabled, so clean up by truncating any verity
 	 * metadata that was written beyond i_size (both from cache and from
 	 * disk) and clearing FI_VERITY_IN_PROGRESS.
 	 *
 	 * Taking i_gc_rwsem[WRITE] is needed to stop f2fs garbage collection
 	 * from re-instantiating cached pages we are truncating (since unlike
 	 * normal file accesses, garbage collection isn't limited by i_size).
 	 */
 	f2fs_down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 	truncate_inode_pages(inode->i_mapping, inode->i_size);
 	err2 = f2fs_truncate(inode);
 	if (err2) {
 		f2fs_err(sbi, "Truncating verity metadata failed (errno=%d)",
 			 err2);
 		set_sbi_flag(sbi, SBI_NEED_FSCK);
 	}
 	f2fs_up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
 	return err ?: err2;
 }

 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, 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,
 };
	// 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)
	{
	struct address_space *mapping = inode->i_mapping;
	const struct address_space_operations *aops = mapping->a_ops;

	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 = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
	if (res)
	return res;

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

	res = aops->write_end(NULL, 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))
	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 = f2fs_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);
	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
	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, err2 = 0;

	/*
	* If an error already occurred (which fs/verity/ signals by passing
	* desc == NULL), then only clean-up is needed.
	*/
	if (desc == NULL)
	goto cleanup;

	/* Append the verity descriptor. */
	err = pagecache_write(inode, desc, desc_size, desc_pos);
	if (err)
	goto cleanup;

	/*
	* Write all pages (both data and verity metadata). Note that this must
	* happen before clearing FI_VERITY_IN_PROGRESS; otherwise pages beyond
	* i_size won't be written properly. For crash consistency, this also
	* must happen before the verity inode flag gets persisted.
	*/
	err = filemap_write_and_wait(inode->i_mapping);
	if (err)
	goto cleanup;

	/* Set the verity xattr. */
	err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
	F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
	NULL, XATTR_CREATE);
	if (err)
	goto cleanup;

	/* Finally, set the verity inode flag. */
	file_set_verity(inode);
	f2fs_set_inode_flags(inode);
	f2fs_mark_inode_dirty_sync(inode, true);

	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
	return 0;

	cleanup:
	/*
	* Verity failed to be enabled, so clean up by truncating any verity
	* metadata that was written beyond i_size (both from cache and from
	* disk) and clearing FI_VERITY_IN_PROGRESS.
	*
	* Taking i_gc_rwsem[WRITE] is needed to stop f2fs garbage collection
	* from re-instantiating cached pages we are truncating (since unlike
	* normal file accesses, garbage collection isn't limited by i_size).
	*/
	f2fs_down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
	truncate_inode_pages(inode->i_mapping, inode->i_size);
	err2 = f2fs_truncate(inode);
	if (err2) {
	f2fs_err(sbi, "Truncating verity metadata failed (errno=%d)",
	err2);
	set_sbi_flag(sbi, SBI_NEED_FSCK);
	}
	f2fs_up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
	return err ?: err2;
	}

	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, 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,
	};