ext4: fix infinite loop when replaying fast_commit

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by unconditionally initializing the structure in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
 fs/ext4/extents_status.c | 2 ++
 1 file changed, 2 insertions(+)

fs/ext4/extents_status.c +2 -0

index 4a00e2f019d9..3a53dbb85e15 100644
@@ -310,6 +310,8 @@ void ext4_es_find_extent_range(struct inode *inode,
 			       ext4_lblk_t lblk, ext4_lblk_t end,
 			       struct extent_status *es)
 {
+	es->es_lblk = es->es_len = es->es_pblk = 0;
+
 	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
 		return;
 

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by unconditionally initializing the structure in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
 fs/ext4/extents_status.c | 2 ++
 1 file changed, 2 insertions(+)

fs/ext4/extents_status.c +2 -0

index 4a00e2f019d9..3a53dbb85e15 100644
@@ -310,6 +310,8 @@ void ext4_es_find_extent_range(struct inode *inode,
 			       ext4_lblk_t lblk, ext4_lblk_t end,
 			       struct extent_status *es)
 {
+	es->es_lblk = es->es_len = es->es_pblk = 0;
+
 	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
 		return;
 

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

[...]