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) <luis.henriques@linux.dev>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20240515082857.32730-1-luis.henriques@linux.dev
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 4a00e2f019d932c8652eada2968ec68d87ac46ad..3a53dbb85e15bd2eb02cc07536725416fed49ee6 100644 (file)
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -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;