ext2: fix block range in ext2_data_block_valid()

For block validity we should check the block range
from start_block to start_block + count - 1, so fix
the range in ext2_data_block_valid() and also modify
the count argument properly in calling place.
Signed-off-by: Chengguang Xu <cgxu519@zoho.com.cn>
Link: https://lore.kernel.org/r/20190723112155.20329-1-cgxu519@zoho.com.cnSigned-off-by: Jan Kara <jack@suse.cz>

fs/ext2/balloc.c

@@ -1203,13 +1203,13 @@ int ext2_data_block_valid(struct ext2_sb_info *sbi, ext2_fsblk_t start_blk,
 			  unsigned int count)
 {
 	if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
-	    (start_blk + count < start_blk) ||
-	    (start_blk > le32_to_cpu(sbi->s_es->s_blocks_count)))
+	    (start_blk + count - 1 < start_blk) ||
+	    (start_blk + count - 1 >= le32_to_cpu(sbi->s_es->s_blocks_count)))
 		return 0;
 
 	/* Ensure we do not step over superblock */
 	if ((start_blk <= sbi->s_sb_block) &&
-	    (start_blk + count >= sbi->s_sb_block))
+	    (start_blk + count - 1 >= sbi->s_sb_block))
 		return 0;
 
 	return 1;

fs/ext2/xattr.c

@@ -794,7 +794,7 @@ ext2_xattr_delete_inode(struct inode *inode)
 	if (!EXT2_I(inode)->i_file_acl)
 		goto cleanup;
 
-	if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 0)) {
+	if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 1)) {
 		ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 			"inode %ld: xattr block %d is out of data blocks range",
 			inode->i_ino, EXT2_I(inode)->i_file_acl);