Re: [bug report] BUG: kernel NULL pointer dereference, address: 0000000000000001

[Ming Lei <ming.lei@redhat.com>]

Hi Changhui,

On Mon, Jun 23, 2025 at 10:58:24AM +0800, Changhui Zhong wrote:
> Hello,
> 
> the following kernel panic was triggered by ubdsrv  generic/002,
> please help check and let me know if you need any info/test, thanks.
> 
> commit HEAD:
> 
> commit 2589cd05008205ee29f5f66f24a684732ee2e3a3
> Merge: 98d0347fe8fb e1c75831f682
> Author: Jens Axboe <axboe@kernel.dk>
> Date:   Wed Jun 18 05:11:50 2025 -0600
> 
>     Merge branch 'io_uring-6.16' into for-next
> 
>     * io_uring-6.16:
>       io_uring: fix potential page leak in io_sqe_buffer_register()
>       io_uring/sqpoll: don't put task_struct on tctx setup failure
>       io_uring: remove duplicate io_uring_alloc_task_context() definition

The above branch has been merged to v6.16-rc3, can you reproduce it with -rc3?

I tried to duplicate in my test VM, not succeed with -rc3.

...

> [ 7044.064528] BUG: kernel NULL pointer dereference, address: 0000000000000001
> [ 7044.071507] #PF: supervisor read access in kernel mode
> [ 7044.076653] #PF: error_code(0x0000) - not-present page
> [ 7044.081801] PGD 462c42067 P4D 462c42067 PUD 462c43067 PMD 0
> [ 7044.087488] Oops: Oops: 0000 [#1] SMP NOPTI
> [ 7044.091685] CPU: 13 UID: 0 PID: 367 Comm: kworker/13:1H Not tainted
> 6.16.0-rc2+ #1 PREEMPT(voluntary)
> [ 7044.100991] Hardware name: Dell Inc. PowerEdge R640/0X45NX, BIOS
> 2.22.2 09/12/2024
> [ 7044.108565] Workqueue: kblockd blk_mq_requeue_work
> [ 7044.113374] RIP: 0010:__io_req_task_work_add+0x18/0x1f0

Can you share where the above line points to source line if it can be
reproduced in -rc3?

gdb> l *(__io_req_task_work_add+0x18)


Thanks,
Ming