ext4: Calculate and verify checksums of extended attribute blocks

Calculate and verify the checksums of extended attribute blocks.  This
only applies to separate EA blocks that are pointed to by
inode->i_file_acl (i.e.  external EA blocks); the checksum lives in
the EA header.
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/xattr.c

@@ -122,6 +122,58 @@ const struct xattr_handler *ext4_xattr_handlers[] = {
 	NULL
 };
 
+static __le32 ext4_xattr_block_csum(struct inode *inode,
+				    sector_t block_nr,
+				    struct ext4_xattr_header *hdr)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	__u32 csum, old;
+
+	old = hdr->h_checksum;
+	hdr->h_checksum = 0;
+	if (le32_to_cpu(hdr->h_refcount) != 1) {
+		block_nr = cpu_to_le64(block_nr);
+		csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&block_nr,
+				   sizeof(block_nr));
+	} else
+		csum = ei->i_csum_seed;
+	csum = ext4_chksum(sbi, csum, (__u8 *)hdr,
+			   EXT4_BLOCK_SIZE(inode->i_sb));
+	hdr->h_checksum = old;
+	return cpu_to_le32(csum);
+}
+
+static int ext4_xattr_block_csum_verify(struct inode *inode,
+					sector_t block_nr,
+					struct ext4_xattr_header *hdr)
+{
+	if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+		EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) &&
+	    (hdr->h_checksum != ext4_xattr_block_csum(inode, block_nr, hdr)))
+		return 0;
+	return 1;
+}
+
+static void ext4_xattr_block_csum_set(struct inode *inode,
+				      sector_t block_nr,
+				      struct ext4_xattr_header *hdr)
+{
+	if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+		EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return;
+
+	hdr->h_checksum = ext4_xattr_block_csum(inode, block_nr, hdr);
+}
+
+static inline int ext4_handle_dirty_xattr_block(handle_t *handle,
+						struct inode *inode,
+						struct buffer_head *bh)
+{
+	ext4_xattr_block_csum_set(inode, bh->b_blocknr, BHDR(bh));
+	return ext4_handle_dirty_metadata(handle, inode, bh);
+}
+
 static inline const struct xattr_handler *
 ext4_xattr_handler(int name_index)
 {
@@ -156,12 +208,22 @@ ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end)
 }
 
 static inline int
-ext4_xattr_check_block(struct buffer_head *bh)
+ext4_xattr_check_block(struct inode *inode, struct buffer_head *bh)
 {
+	int error;
+
+	if (buffer_verified(bh))
+		return 0;
+
 	if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
 	    BHDR(bh)->h_blocks != cpu_to_le32(1))
 		return -EIO;
-	return ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
+	if (!ext4_xattr_block_csum_verify(inode, bh->b_blocknr, BHDR(bh)))
+		return -EIO;
+	error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
+	if (!error)
+		set_buffer_verified(bh);
+	return error;
 }
 
 static inline int
@@ -224,7 +286,7 @@ ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
 		goto cleanup;
 	ea_bdebug(bh, "b_count=%d, refcount=%d",
 		atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
-	if (ext4_xattr_check_block(bh)) {
+	if (ext4_xattr_check_block(inode, bh)) {
 bad_block:
 		EXT4_ERROR_INODE(inode, "bad block %llu",
 				 EXT4_I(inode)->i_file_acl);
@@ -369,7 +431,7 @@ ext4_xattr_block_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 		goto cleanup;
 	ea_bdebug(bh, "b_count=%d, refcount=%d",
 		atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
-	if (ext4_xattr_check_block(bh)) {
+	if (ext4_xattr_check_block(inode, bh)) {
 		EXT4_ERROR_INODE(inode, "bad block %llu",
 				 EXT4_I(inode)->i_file_acl);
 		error = -EIO;
@@ -492,7 +554,7 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode,
 		if (ce)
 			mb_cache_entry_release(ce);
 		unlock_buffer(bh);
-		error = ext4_handle_dirty_metadata(handle, inode, bh);
+		error = ext4_handle_dirty_xattr_block(handle, inode, bh);
 		if (IS_SYNC(inode))
 			ext4_handle_sync(handle);
 		dquot_free_block(inode, 1);
@@ -662,7 +724,7 @@ ext4_xattr_block_find(struct inode *inode, struct ext4_xattr_info *i,
 		ea_bdebug(bs->bh, "b_count=%d, refcount=%d",
 			atomic_read(&(bs->bh->b_count)),
 			le32_to_cpu(BHDR(bs->bh)->h_refcount));
-		if (ext4_xattr_check_block(bs->bh)) {
+		if (ext4_xattr_check_block(inode, bs->bh)) {
 			EXT4_ERROR_INODE(inode, "bad block %llu",
 					 EXT4_I(inode)->i_file_acl);
 			error = -EIO;
@@ -725,7 +787,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			if (error == -EIO)
 				goto bad_block;
 			if (!error)
-				error = ext4_handle_dirty_metadata(handle,
+				error = ext4_handle_dirty_xattr_block(handle,
 								      inode,
 								      bs->bh);
 			if (error)
@@ -796,7 +858,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 				ea_bdebug(new_bh, "reusing; refcount now=%d",
 					le32_to_cpu(BHDR(new_bh)->h_refcount));
 				unlock_buffer(new_bh);
-				error = ext4_handle_dirty_metadata(handle,
+				error = ext4_handle_dirty_xattr_block(handle,
 								      inode,
 								      new_bh);
 				if (error)
@@ -855,7 +917,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			set_buffer_uptodate(new_bh);
 			unlock_buffer(new_bh);
 			ext4_xattr_cache_insert(new_bh);
-			error = ext4_handle_dirty_metadata(handle,
+			error = ext4_handle_dirty_xattr_block(handle,
 							      inode, new_bh);
 			if (error)
 				goto cleanup;
@@ -1193,7 +1255,7 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
 		error = -EIO;
 		if (!bh)
 			goto cleanup;
-		if (ext4_xattr_check_block(bh)) {
+		if (ext4_xattr_check_block(inode, bh)) {
 			EXT4_ERROR_INODE(inode, "bad block %llu",
 					 EXT4_I(inode)->i_file_acl);
 			error = -EIO;