ext4: refactor __ext4_check_dir_entry() to accept start and size

The __ext4_check_dir_entry() function() is used to check whether the
de is over the block boundary.  Now with inline data, it could be
within the block boundary while exceeds the inode size.  So check this
function to check the overflow more precisely.
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/dir.c

@@ -72,7 +72,7 @@ static int is_dx_dir(struct inode *inode)
 int __ext4_check_dir_entry(const char *function, unsigned int line,
 			   struct inode *dir, struct file *filp,
 			   struct ext4_dir_entry_2 *de,
-			   struct buffer_head *bh,
+			   struct buffer_head *bh, char *buf, int size,
 			   unsigned int offset)
 {
 	const char *error_msg = NULL;
@@ -85,9 +85,8 @@ int __ext4_check_dir_entry(const char *function, unsigned int line,
 		error_msg = "rec_len % 4 != 0";
 	else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
 		error_msg = "rec_len is too small for name_len";
-	else if (unlikely(((char *) de - bh->b_data) + rlen >
-			  dir->i_sb->s_blocksize))
-		error_msg = "directory entry across blocks";
+	else if (unlikely(((char *) de - buf) + rlen > size))
+		error_msg = "directory entry across range";
 	else if (unlikely(le32_to_cpu(de->inode) >
 			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
 		error_msg = "inode out of bounds";
@@ -98,14 +97,14 @@ int __ext4_check_dir_entry(const char *function, unsigned int line,
 		ext4_error_file(filp, function, line, bh->b_blocknr,
 				"bad entry in directory: %s - offset=%u(%u), "
 				"inode=%u, rec_len=%d, name_len=%d",
-				error_msg, (unsigned) (offset % bh->b_size),
+				error_msg, (unsigned) (offset % size),
 				offset, le32_to_cpu(de->inode),
 				rlen, de->name_len);
 	else
 		ext4_error_inode(dir, function, line, bh->b_blocknr,
 				"bad entry in directory: %s - offset=%u(%u), "
 				"inode=%u, rec_len=%d, name_len=%d",
-				error_msg, (unsigned) (offset % bh->b_size),
+				error_msg, (unsigned) (offset % size),
 				offset, le32_to_cpu(de->inode),
 				rlen, de->name_len);
 
@@ -221,8 +220,9 @@ static int ext4_readdir(struct file *filp,
 		while (!error && filp->f_pos < inode->i_size
 		       && offset < sb->s_blocksize) {
 			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
-			if (ext4_check_dir_entry(inode, filp, de,
-						 bh, offset)) {
+			if (ext4_check_dir_entry(inode, filp, de, bh,
+						 bh->b_data, bh->b_size,
+						 offset)) {
 				/*
 				 * On error, skip the f_pos to the next block
 				 */

fs/ext4/ext4.h

@@ -1960,10 +1960,11 @@ ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
 extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
 				  struct file *,
 				  struct ext4_dir_entry_2 *,
-				  struct buffer_head *, unsigned int);
-#define ext4_check_dir_entry(dir, filp, de, bh, offset)			\
+				  struct buffer_head *, char *, int,
+				  unsigned int);
+#define ext4_check_dir_entry(dir, filp, de, bh, buf, size, offset)	\
 	unlikely(__ext4_check_dir_entry(__func__, __LINE__, (dir), (filp), \
-					(de), (bh), (offset)))
+					(de), (bh), (buf), (size), (offset)))
 extern int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
 				    __u32 minor_hash,
 				    struct ext4_dir_entry_2 *dirent);

fs/ext4/namei.c

@@ -892,6 +892,7 @@ static int htree_dirblock_to_tree(struct file *dir_file,
 					   EXT4_DIR_REC_LEN(0));
 	for (; de < top; de = ext4_next_entry(de, dir->i_sb->s_blocksize)) {
 		if (ext4_check_dir_entry(dir, NULL, de, bh,
+				bh->b_data, bh->b_size,
 				(block<<EXT4_BLOCK_SIZE_BITS(dir->i_sb))
 					 + ((char *)de - bh->b_data))) {
 			/* On error, skip the f_pos to the next block. */
@@ -1130,7 +1131,8 @@ static inline int search_dirblock(struct buffer_head *bh,
 		if ((char *) de + namelen <= dlimit &&
 		    ext4_match (namelen, name, de)) {
 			/* found a match - just to be sure, do a full check */
-			if (ext4_check_dir_entry(dir, NULL, de, bh, offset))
+			if (ext4_check_dir_entry(dir, NULL, de, bh, bh->b_data,
+						 bh->b_size, offset))
 				return -1;
 			*res_dir = de;
 			return 1;
@@ -1643,7 +1645,8 @@ static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,
 		de = (struct ext4_dir_entry_2 *)bh->b_data;
 		top = bh->b_data + (blocksize - csum_size) - reclen;
 		while ((char *) de <= top) {
-			if (ext4_check_dir_entry(dir, NULL, de, bh, offset))
+			if (ext4_check_dir_entry(dir, NULL, de, bh, bh->b_data,
+						 bh->b_size, offset))
 				return -EIO;
 			if (ext4_match(namelen, name, de))
 				return -EEXIST;
@@ -2076,7 +2079,8 @@ static int ext4_delete_entry(handle_t *handle,
 	pde = NULL;
 	de = (struct ext4_dir_entry_2 *) bh->b_data;
 	while (i < bh->b_size - csum_size) {
-		if (ext4_check_dir_entry(dir, NULL, de, bh, i))
+		if (ext4_check_dir_entry(dir, NULL, de, bh,
+					 bh->b_data, bh->b_size, i))
 			return -EIO;
 		if (de == de_del)  {
 			BUFFER_TRACE(bh, "get_write_access");
@@ -2439,7 +2443,8 @@ static int empty_dir(struct inode *inode)
 			set_buffer_verified(bh);
 			de = (struct ext4_dir_entry_2 *) bh->b_data;
 		}
-		if (ext4_check_dir_entry(inode, NULL, de, bh, offset)) {
+		if (ext4_check_dir_entry(inode, NULL, de, bh,
+					 bh->b_data, bh->b_size, offset)) {
 			de = (struct ext4_dir_entry_2 *)(bh->b_data +
 							 sb->s_blocksize);
 			offset = (offset | (sb->s_blocksize - 1)) + 1;