linux-kernel - Re: [syzbot] [io-uring?] BUG: unable to handle kernel NULL pointer dereference in io_buffer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <69ae835b-89b2-44bf-b51c-c365d89dbb45@kernel.dk>
Date: Mon, 12 May 2025 08:19:47 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Pavel Begunkov <asml.silence@...il.com>,
 syzbot <syzbot+6456a99dfdc2e78c4feb@...kaller.appspotmail.com>,
 io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [io-uring?] BUG: unable to handle kernel NULL pointer
 dereference in io_buffer_select

On 5/12/25 8:19 AM, Pavel Begunkov wrote:
> On 5/12/25 14:56, Jens Axboe wrote:
>> On 5/11/25 6:22 AM, Pavel Begunkov wrote:
>>> On 5/11/25 01:19, syzbot wrote:
> ...>> this line:
>>>
>>> tail = smp_load_acquire(&br->tail);
>>>
>>> The offset of the tail field is 0xe so bl->buf_ring should be 0. That's
>>> while it has IOBL_BUF_RING flag set. Same goes for the other report. Also,
>>> since it's off io_buffer_select(), which looks up the list every time we
>>> can exclude the req having a dangling pointer.
>>
>> It's funky for sure, the other one is regular classic provided buffers.
>> Interestingly, both reports are for arm32...
> 
> The other is ring pbuf as well

True yes, both are pbuf. I can't hit any of this on arm64 or x86-64, fwiw.
Which is why I thought the arm32 connection might be interesting. Not that
the arch should matter at all here, but...

-- 
Jens Axboe