Re: [PATCH v2] ocfs2: Fix shift-out-of-bounds UBSAN bug in ocfs2_verify_volume()

[Joseph Qi]

On 8/20/24 9:03 AM, qasdev wrote:
> On Mon, Aug 19, 2024 at 10:52:29AM +0800, Joseph Qi wrote:
>>
>>
>> On 8/18/24 7:43 PM, Heming Zhao wrote:
>>> On 8/16/24 21:41, qasdev wrote:
>>>>  From ad1ca2fd2ecf4eb7ec2c76fcbbf34639f0ad87ca Mon Sep 17 00:00:00 2001
>>>> From: Qasim Ijaz <qasdev00@xxxxxxxxx>
>>>> Date: Fri, 16 Aug 2024 02:30:25 +0100
>>>> Subject: [PATCH] ocfs2: Fix shift-out-of-bounds UBSAN bug in
>>>>   ocfs2_verify_volume()
>>>>
>>
>> The above should be eliminated from patch body. 
>>
>>>> This patch addresses a shift-out-of-bounds error in the
>>>> ocfs2_verify_volume() function, identified by UBSAN. The bug was triggered
>>>> by an invalid s_clustersize_bits value (e.g., 1548), which caused the
>>>> expression "1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits)"
>>>> to exceed the limits of a 32-bit integer,
>>>> leading to an out-of-bounds shift.
>>>>
>>>> Reported-by: syzbot <syzbot+f3fff775402751ebb471@xxxxxxxxxxxxxxxxxxxxxxxxx>
>>>> Closes: https://syzkaller.appspot.com/bug?extid=f3fff775402751ebb471
>>>> Tested-by: syzbot <syzbot+f3fff775402751ebb471@xxxxxxxxxxxxxxxxxxxxxxxxx>
>>>> Signed-off-by: Qasim Ijaz <qasdev00@xxxxxxxxx>
>>>> ---
>>>>   fs/ocfs2/super.c | 8 ++++++--
>>>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
>>>> index afee70125ae3..1e43cdca7f40 100644
>>>> --- a/fs/ocfs2/super.c
>>>> +++ b/fs/ocfs2/super.c
>>>> @@ -2357,8 +2357,12 @@ static int ocfs2_verify_volume(struct ocfs2_dinode *di,
>>>>                    (unsigned long long)bh->b_blocknr);
>>>>           } else if (le32_to_cpu(di->id2.i_super.s_clustersize_bits) < 12 ||
>>>>                   le32_to_cpu(di->id2.i_super.s_clustersize_bits) > 20) {
>>>> -            mlog(ML_ERROR, "bad cluster size found: %u\n",
>>>> -                 1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits));
>>>> +            if (le32_to_cpu(di->id2.i_super.s_clustersize_bits) < 32)
>>>> +                mlog(ML_ERROR, "bad cluster size found: %u\n",
>>>> +                     1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits));
>>>> +            else
>>>> +                mlog(ML_ERROR, "invalid cluster size bit value: %u\n",
>>>> +                     le32_to_cpu(di->id2.i_super.s_clustersize_bits));
>>>
>>> I prefer to use concise code to fix the error.
>>> Do you like below code?
>>> -        mlog(ML_ERROR, "bad cluster size found: %u\n",
>>> -                 1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits));
>>> +        mlog(ML_ERROR, "bad cluster size bit found: %u\n",
>>> +                 le32_to_cpu(di->id2.i_super.s_clustersize_bits));
>>>
>>
>> Agree. qasdev, Could you please update and send v2?
>>
>> Thanks,
>> Joseph
> 
> Thanks for the feedback. After considering the input, I've refined the patch 
> to make it more concise. I've updated the patch and included it below:
> 
Hi, please send v2 as a standalone thread.

Thanks,
Joseph