[Crash-utility] [PATCH] SLUB: Fix for offset change of struct slab members on Linux 6.2-rc1

[lijiang]

On Mon, Dec 26, 2022 at 12:42 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab at nec.com>
wrote:

> On 2022/12/22 16:50, lijiang wrote:
> > After applying the patch, I got another error based on the latest kernel
> > commit 9d2f6060fe4c3b49d0cdc1dce1c99296f33379c8:
> >
> >   crash> kmem -S filp
> > CACHE             OBJSIZE  ALLOCATED     TOTAL  SLABS  SSIZE  NAME
> > ffff9d80c030a100      232       1125      3936    123     8k  filp
> > CPU 0 KMEM_CACHE_CPU:
> >    ffff9d81e7a38470
> > CPU 0 SLAB:
> >    SLAB              MEMORY            NODE  TOTAL  ALLOCATED  FREE
> >    fffff0f3841a7700  ffff9d80c69dc000     0     32         10    22
> >    FREE / [ALLOCATED]
> > kmem: filp: slab: fffff0f3841a7700 invalid freepointer: 4404c55079ecb7fe
> > CPU 1 KMEM_CACHE_CPU:
> >    ffff9d81e7a78470
> > CPU 1 SLAB:
> >    SLAB              MEMORY            NODE  TOTAL  ALLOCATED  FREE
> >    fffff0f38446a600  ffff9d80d1a98000     0     32          0    32
> >    FREE / [ALLOCATED]
> > ...
> >
> > And this issue can not always be reproduced, I have tested it more than
> ten
> > times, the above error can be observed on my side, maybe one or two
> times.
> >
> > But anyway, I'm curious if this is another issue. Could you please also
> > double check it?
>
> Thank you for testing.
>
> I have not reproduced it with kdump, but did it with live system when
> repeating this:
>
> crash> kmem -S > /tmp/kmem-S
> crash> kmem -S > /tmp/kmem-S
> ...
> crash> kmem -S > /tmp/kmem-S
> kmem: kmalloc-16: slab: ffffdb3bc440bcc0 invalid freepointer:
> d3ec64863a077e7c
>
> As you say, it does not always happen, so it will be a timing issue or
> corner case.  Maybe there was a change in managing freepointer list,
> but so far I'm not sure what the cause is.
>
>
Theoretically, this issue can also be reproduced on kdump at a certain time
point.


> Anyway, I think it's not due to the offset change of slab.slab_list and
> not the same issue.  Can we apply this and look into it later?
>
>
Yes, I agree that it might be another issue. Let's leave it there.
For the patch: Ack.

Thanks.
Lianbo

Thanks,
> Kazu
>
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