Re: [PATCH] ext4: Fix KASAN use-after-free in ext4_find_extent

[Baokun Li]

Hi,

On 2025-12-09 20:27, 余昊铖 wrote:
> Hello,
>
>
> I would like to report a potential security issue in the Linux kernel ext4 filesystem, which I found using a modified syzkaller-based kernel fuzzing tool that I developed.
>
I noticed that your configuration has CONFIG_BLK_DEV_WRITE_MOUNTED enabled.

This setting allows bare writes to an already mounted ext4 filesystem,
meaning certain ext4 metadata (like extent tree blocks) can be modified
without the filesystem being aware of the changes.

Could you please try disabling CONFIG_BLK_DEV_WRITE_MOUNTED and see
if the issue is still reproducible?


Cheers,
Baokun