ext4: Validate extent details only when read from the disk

Make sure we validate extent details only when read from the disk.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Thiemo Nagel <thiemo.nagel@ph.tum.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4_extents.h

@@ -241,5 +241,6 @@ extern int ext4_ext_search_left(struct inode *, struct ext4_ext_path *,
 extern int ext4_ext_search_right(struct inode *, struct ext4_ext_path *,
 						ext4_lblk_t *, ext4_fsblk_t *);
 extern void ext4_ext_drop_refs(struct ext4_ext_path *);
+extern int ext4_ext_check_inode(struct inode *inode);
 #endif /* _EXT4_EXTENTS */
 

fs/ext4/extents.c

@@ -429,6 +429,11 @@ corrupted:
 #define ext4_ext_check(inode, eh, depth)	\
 	__ext4_ext_check(__func__, inode, eh, depth)
 
+int ext4_ext_check_inode(struct inode *inode)
+{
+	return ext4_ext_check(inode, ext_inode_hdr(inode), ext_depth(inode));
+}
+
 #ifdef EXT_DEBUG
 static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
 {
@@ -631,9 +636,6 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
 
 	eh = ext_inode_hdr(inode);
 	depth = ext_depth(inode);
-	if (ext4_ext_check(inode, eh, depth))
-		return ERR_PTR(-EIO);
-
 
 	/* account possible depth increase */
 	if (!path) {
@@ -649,6 +651,8 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
 	i = depth;
 	/* walk through the tree */
 	while (i) {
+		int need_to_validate = 0;
+
 		ext_debug("depth %d: num %d, max %d\n",
 			  ppos, le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
 
@@ -657,10 +661,17 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
 		path[ppos].p_depth = i;
 		path[ppos].p_ext = NULL;
 
-		bh = sb_bread(inode->i_sb, path[ppos].p_block);
-		if (!bh)
+		bh = sb_getblk(inode->i_sb, path[ppos].p_block);
+		if (unlikely(!bh))
 			goto err;
-
+		if (!bh_uptodate_or_lock(bh)) {
+			if (bh_submit_read(bh) < 0) {
+				put_bh(bh);
+				goto err;
+			}
+			/* validate the extent entries */
+			need_to_validate = 1;
+		}
 		eh = ext_block_hdr(bh);
 		ppos++;
 		BUG_ON(ppos > depth);
@@ -668,7 +679,7 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
 		path[ppos].p_hdr = eh;
 		i--;
 
-		if (ext4_ext_check(inode, eh, i))
+		if (need_to_validate && ext4_ext_check(inode, eh, i))
 			goto err;
 	}
 

fs/ext4/inode.c

@@ -4345,6 +4345,16 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 			(__u64)(le32_to_cpu(raw_inode->i_version_hi)) << 32;
 	}
 
+	if (ei->i_flags & EXT4_EXTENTS_FL) {
+		/* Validate extent which is part of inode */
+		ret = ext4_ext_check_inode(inode);
+		if (ret) {
+			brelse(bh);
+			goto bad_inode;
+		}
+
+	}
+
 	if (S_ISREG(inode->i_mode)) {
 		inode->i_op = &ext4_file_inode_operations;
 		inode->i_fop = &ext4_file_operations;