Commit b05addf6 authored by Pratyush Yadav's avatar Pratyush Yadav Committed by Andrew Morton
Browse files

kho: warn and exit when unpreserved page wasn't preserved 

Calling __kho_unpreserve() on a pair of (pfn, end_pfn) that wasn't
preserved is a bug.  Currently, if that is done, the physxa or bits can be
NULL.  This results in a soft lockup since a NULL physxa or bits results
in redoing the loop without ever making any progress.

Return when physxa or bits are not found, but WARN first to loudly
indicate invalid behaviour.

Link: https://lkml.kernel.org/r/20251103180235.71409-3-pratyush@kernel.org


Fixes: fc33e4b4 ("kexec: enable KHO support for memory preservation")
Signed-off-by: default avatarPratyush Yadav <pratyush@kernel.org>
Reviewed-by: default avatarMike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7ecd2e43

kernel/kexec_handover.c

+4 −4
Original line number Diff line number Diff line
@@ -171,12 +171,12 @@ static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn, 
		const unsigned long pfn_high = pfn >> order;



		physxa = xa_load(&track->orders, order);

		if (!physxa)

			continue;

		if (WARN_ON_ONCE(!physxa))

			return;



		bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);

		if (!bits)

			continue;

		if (WARN_ON_ONCE(!bits))

			return;



		clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);