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

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Message-ID: <b7604342-1d56-1c15-1526-380a4fdbbb41@kernel.org>
Date:   Sun, 16 Apr 2023 22:33:36 +0800
From:   Chao Yu <chao@...nel.org>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>,
        linux-erofs@...ts.ozlabs.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        syzbot+aafb3f37cfeb6534c4ac@...kaller.appspotmail.com
Subject: Re: [PATCH] erofs: stop parsing non-compact HEAD index if clusterofs
 is invalid

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@...kaller.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@...ux.alibaba.com>

Reviewed-by: Chao Yu <chao@...nel.org>

Thanks,