Re: [PATCH] erofs: fix use-after-free on sbi->sync_decompress

[Chao Yu]

On 5/22/26 16:27, Gao Xiang wrote:
> z_erofs_decompress_kickoff() can race with filesystem unmount, causing
> a use-after-free on sbi->sync_decompress.
>
> When I/O completes, z_erofs_endio() calls z_erofs_decompress_kickoff()
> to queue z_erofs_decompressqueue_work() asynchronously. Then, after all
> folios are unlocked, unmount workflow can proceed and sbi will be freed
> before accessing to sbi->sync_decompress.
>
> Thread (unmount)        I/O completion        kworker
>                          queue_work
>                                                z_erofs_decompressqueue_work
>                                                 (all folios are unlocked)
> cleanup_mnt
>   ..
>   erofs_kill_sb
>    erofs_sb_free
>     kfree(sbi)
>                          access sbi->sync_decompress  // UAF!!
>
> Fixes: 40452ffca3c1 ("erofs: add sysfs node to control sync decompression strategy")
> Reported-by: syzbot+52bae5c495dbe261a0bc@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=52bae5c495dbe261a0bc
> Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>

Reviewed-by: Chao Yu <chao@xxxxxxxxxx>

Thanks,