ext4: avoid a potential overflow in ext4_es_can_be_merged()

Check the length of an extent to avoid a potential overflow in
ext4_es_can_be_merged().

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Dmitry Monakhov <dmonakhov@openvz.org>

1 files changed, 15 insertions, 5 deletions

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 95796a1b7522..37f9a2d8fd04 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -333,17 +333,27 @@ static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
 static int ext4_es_can_be_merged(struct extent_status *es1,
                                  struct extent_status *es2)
 {
-        if (es1->es_lblk + es1->es_len != es2->es_lblk)
+        if (ext4_es_status(es1) != ext4_es_status(es2))
                 return 0;
 
-        if (ext4_es_status(es1) != ext4_es_status(es2))
+        if (((__u64) es1->es_len) + es2->es_len > 0xFFFFFFFFULL)
                 return 0;
 
-        if ((ext4_es_is_written(es1) || ext4_es_is_unwritten(es1)) &&
-            (ext4_es_pblock(es1) + es1->es_len != ext4_es_pblock(es2)))
+        if (((__u64) es1->es_lblk) + es1->es_len != es2->es_lblk)
                 return 0;
 
-        return 1;
+        if ((ext4_es_is_written(es1) || ext4_es_is_unwritten(es1)) &&
+            (ext4_es_pblock(es1) + es1->es_len == ext4_es_pblock(es2)))
+                return 1;
+
+        if (ext4_es_is_hole(es1))
+                return 1;
+
+        /* we need to check delayed extent is without unwritten status */
+        if (ext4_es_is_delayed(es1) && !ext4_es_is_unwritten(es1))
+                return 1;
+
+        return 0;
 }
 
 static struct extent_status *