From b05addf6f0596edb1f82ab4059438c7ef2d2686d Mon Sep 17 00:00:00 2001 From: Pratyush Yadav Date: Mon, 3 Nov 2025 19:02:32 +0100 Subject: [PATCH] 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: fc33e4b44b27 ("kexec: enable KHO support for memory preservation") Signed-off-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) Cc: Alexander Graf Cc: Baoquan He Cc: Pasha Tatashin Cc: Signed-off-by: Andrew Morton --- kernel/kexec_handover.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c index e0bafe7c0ded..03d12e27189f 100644 --- a/kernel/kexec_handover.c +++ b/kernel/kexec_handover.c @@ -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); -- 2.47.3