Re: [tip:sched/core] [sched/fair] 79104becf4: BUG:kernel_NULL_pointer_dereference,address

[Chen, Yu C]

On 10/27/2025 10:09 PM, Peter Zijlstra wrote:
> On Mon, Oct 27, 2025 at 03:07:18PM +0100, Peter Zijlstra wrote:
> > On Mon, Oct 27, 2025 at 02:55:16PM +0100, Peter Zijlstra wrote:
> >
> > > > May I know if you are using the kernel config 0day attached?
> > > > I found that the config 0day attached
> > > > (https://download.01.org/0day-ci/archive/20251021/202510211205.1e0f5223-lkp@xxxxxxxxx/config-6.18.0-rc1-00001-g79104becf42b)
> > > > has
> > > > CONFIG_IA32_EMULATION=y
> > > > CONFIG_IA32_EMULATION_DEFAULT_DISABLED=y
> >
> > Yep, deleting that entry makes it all work.
>
> 'work' might be over stating, it boots and starts trinity, which then
> promptly (as in a handful of seconds) triggers OOM and dies. Not
> actually reproducing the NULL deref I was looking for.

Change the following line in job-script
export memory='16G'
to
export memory='64G'
?

I had a try and can reproduce the NULL except at first run:

[  137.151416][  T321] BUG: kernel NULL pointer dereference, address: 
0000000000000051
[  137.152128][  T321] #PF: supervisor read access in kernel mode
[  137.152661][  T321] #PF: error_code(0x0000) - not-present page
[  137.153155][  T321] PGD 100b76067 P4D 100b76067 PUD 115fd6067 PMD 0
[  137.153834][  T321] Oops: Oops: 0000 [#1]
[  137.154256][  T321] CPU: 0 UID: 65534 PID: 321 Comm: trinity-c1 Not 
tainted 6.18.0-rc1-g30682ad76ee6 #4 PREEMPT
[  137.155384][  T321] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + 
PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[  137.156509][  T321] RIP: 0010:pick_task_fair+0x69/0x9d


thanks,
Chenyu