[PATCH] ext4: fix infinite loop caused by integer overflow

[Luis Henriques (SUSE)]

An integer overflow will happen if the extent_status len is set to
EXT_MAX_BLOCKS (0xffffffff).  This may cause an infinite loop in function
ext4_ext_determine_insert_hole(), easily reproducible using fstest
generic/039.

Fixes: 6430dea07e85 ("ext4: correct the hole length returned by ext4_map_blocks()")
Signed-off-by: Luis Henriques (SUSE) <luis.henriques@xxxxxxxxx>
---
 fs/ext4/extents.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index e57054bdc5fd..193121b394f9 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4064,7 +4064,7 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 	 * There's a delalloc extent in the hole, handle it if the delalloc
 	 * extent is in front of, behind and straddle the queried range.
 	 */
-	if (lblk >= es.es_lblk + es.es_len) {
+	if (lblk >= ((__u64) es.es_lblk) + es.es_len) {
 		/*
 		 * The delalloc extent is in front of the queried range,
 		 * find again from the queried start block.