[Crash-utility] [PATCH 2/2] Fix "kmem -s|-S" not working properly when CONFIG_SLAB_FREELIST_HARDENED is enabled

[lijiang]

On Thu, Aug 17, 2023 at 8:29 AM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab at nec.com>
wrote:

> On 2023/08/14 10:54, Lianbo Jiang wrote:
> > Currently, crash-utility still depends on detecting the kernel version,
> > or the asm instruction 'bswap' on X86 64/X86 architectures to decide how
> > to deal with the freelist ptr obfuscation, when kernel option
> > CONFIG_SLAB_FREELIST_HARDENED is enabled.
> >
> > As you known, the bit diffusion for freelist ptr obfuscation has
> > experienced the changes several times on the kernel side, For most
> > distributions, usually they might backport these kernel patches from
> > upstream, especially for the old kernel, the 'kmem -s|-S' will fail with
> > an error "invalid freepointer", which can be observed on ppc64le and
> > S390x architectures, etc. That is really not friendly.
> >
> > Given that, let's fix the above issues this time, and it won't rely
> > on the linux version number or asm instruction 'bswap' to decide how to
> > dereference the freelist ptr.
> >
> > Reported-by: Lucas Oakley <soakley at redhat.com>
> > Signed-off-by: Lianbo Jiang <lijiang at redhat.com>
>
> Thank you for the fix.
>
> Maybe we don't have to revert that patch and can use both of the bswap
> way and this way, but seems no big benefit with it, so agree to revert it.
>
>
You are right, Kazu. That is also why I would like to revert the patch
first.

Also thank you for helping with the test, Rafael and Lucas.

Thanks.
Lianbo
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