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

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

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.

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