[PATCH] erofs: stop parsing non-compact HEAD index if clusterofs is invalid

[Chao Yu]

On 2023/4/11 1:37, Gao Xiang wrote:
> Syzbot generated a crafted image [1] with a non-compact HEAD index of
> clusterofs 33024 while valid numbers should be 0 ~ lclustersize-1,
> which causes the following unexpected behavior as below:
> 
>   BUG: unable to handle page fault for address: fffff52101a3fff9
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 23ffed067 P4D 23ffed067 PUD 0
>   Oops: 0000 [#1] PREEMPT SMP KASAN
>   CPU: 1 PID: 4398 Comm: kworker/u5:1 Not tainted 6.3.0-rc6-syzkaller-g09a9639e56c0 #0
>   Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
>   Workqueue: erofs_worker z_erofs_decompressqueue_work
>   RIP: 0010:z_erofs_decompress_queue+0xb7e/0x2b40
>   ...
>   Call Trace:
>    <TASK>
>    z_erofs_decompressqueue_work+0x99/0xe0
>    process_one_work+0x8f6/0x1170
>    worker_thread+0xa63/0x1210
>    kthread+0x270/0x300
>    ret_from_fork+0x1f/0x30
> 
> Note that normal images or images using compact indexes are not
> impacted.  Let's fix this now.
> 
> [1] https://lore.kernel.org/r/000000000000ec75b005ee97fbaa@google.com
> 
> Reported-by: syzbot+aafb3f37cfeb6534c4ac at syzkaller.appspotmail.com
> Fixes: 02827e1796b3 ("staging: erofs: add erofs_map_blocks_iter")
> Fixes: 152a333a5895 ("staging: erofs: add compacted compression indexes support")
> Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>

Reviewed-by: Chao Yu <chao at kernel.org>

Thanks,