Re: [PATCH 1/2] powerpc/kdump: fix KASAN sanitization flag for core_$(BITS).o

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 29/03/26 07:26, Ritesh Harjani (IBM) wrote:
> Sourabh Jain <sourabhjain@linux.ibm.com> writes:
>
>> KASAN instrumentation is intended to be disabled for the kexec core
>> code, but the existing Makefile entry misses the object suffix. As a
>> result, the flag is not applied correctly to core_$(BITS).o.
>>
>> So when KASAN is enabled, kexec_copy_flush and copy_segments in
>> kexec/core_64.c are instrumented, which can result in accesses to
>> shadow memory via normal address translation paths. Since these run
>> with the MMU disabled, such accesses may trigger page faults
>> (bad_page_fault) that cannot be handled in the kdump path, ultimately
>> causing a hang and preventing the kdump kernel from booting. The same
>> is true for kexec as well, since the same functions are used there.
>>
>> Update the entry to include the “.o” suffix so that KASAN
>> instrumentation is properly disabled for this object file.
>>
>> Fixes: 2ab2d5794f14 ("powerpc/kasan: Disable address sanitization in kexec paths")
>> Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
>> Closes: https://lore.kernel.org/all/1dee8891-8bcc-46b4-93f3-fc3a774abd5b@linux.ibm.com/
> Nice catch. Indeed seems to be missed in the Fixes patch.
>
> I think you might want to Cc: stable too, so that it is auto backported
> to previous stable kernel releases too. The Fixes patch was added in
> v5.19 kernel, maybe we weren't testing KASAN + Kdump, but it's worth
> backporting to all stable kernel releases, IMO.

Yes, it is worth backporting this to the stable trees. I will update it 
in v2.

>
> LGTM, please feel free to add:
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>

Thanks for the review Ritesh.

- Sourabh Jain