[PATCH v2] ext4: fix infinite loop when replaying fast_commit

[PATCH v2] ext4: fix infinite loop when replaying fast_commit

[Luis Henriques (SUSE)]

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

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 4a00e2f019d9..3a53dbb85e15 100644
--- 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;
 

Re: [PATCH v2] ext4: fix infinite loop when replaying fast_commit

[Zhang Yi]

On 2024/5/15 16:28, Luis Henriques (SUSE) wrote:
> 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>

Thanks for fixing this issue，looks good to me.

Reviewed-by: Zhang Yi <yi.zhang@huawei.com>

> ---
>  fs/ext4/extents_status.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 4a00e2f019d9..3a53dbb85e15 100644
> --- 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;
>  
>