Re: [PATCH v2] rseq: fix using an uninitialized stack variable in rseq_exit_user_update

[Tetsuo Handa]

On 2026/06/20 4:32, Thomas Gleixner wrote:
> %On Fri, Jun 19 2026 at 21:45, Tetsuo Handa wrote:
>> On 2026/06/02 19:42, Peter Zijlstra wrote:
>>> On Tue, Jun 02, 2026 at 11:08:54AM +0800, Qing Wang wrote:
>>>> There is an bug which is an uninitialized stack variable use in
>>>> `rseq_exit_user_update()` reported by syzbot:
>>>>
>>>> BUG: KMSAN: kernel-infoleak in rseq_set_ids_get_csaddr include/linux/rseq_entry.h:502 [inline]
>>>>
>>>> The local variable:
>>>> ```c
>>>> 	struct rseq_ids ids = {
>>>> 		.cpu_id	 = task_cpu(t),
>>>> 		.mm_cid	 = task_mm_cid(t),
>>>> 		.node_id = cpu_to_node(ids.cpu_id),
>>>> 	};
>>>> ```
>>>
>>> FWIW, I've no idea what that ``` nonsense is, but it does not belong in
>>> Changelogs. I've removed it.
>>>
>>
>> It seems that this problem is still happening after
>> commit 6d99479799c6 ("rseq: Fix using an uninitialized stack variable
>> in rseq_exit_user_update()") was applied. Please check.
> 
> It seems is not really helpful. If you observe the problem can you
> please provide the full debug splat?

Please fetch the full debug splat from https://syzkaller.appspot.com/bug?extid=185a631927096f9da2fc .
This problem is still happening as of commit 9ecfb2f7287a which includes commit 6d99479799c6.