2024-05-15 08:29:12

by Luis Henriques

Subject: [PATCH v2] 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(+)

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;

2024-05-15 12:28:10

by Zhang Yi

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

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) <[email protected]>

Thanks for fixing this issue，looks good to me.

Reviewed-by: Zhang Yi <[email protected]>

> ---
> 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;
>
>