From 3a0b8fa2eb36afc88b62a95f33f0c77c71fa5ded Mon Sep 17 00:00:00 2001 From: "Pratyush Yadav (Google)" Date: Mon, 27 Jul 2026 17:02:39 +0200 Subject: [PATCH] kho: fix size calculation in kho_preserved_memory_reserve() kho_preserved_memory_reserve() calculates the size of a preservation by doing 1 << (order + PAGE_SHIFT). Since the '1' is a 32-bit integer, it can only be shifted by 31. That is, it will only work for preservations up to 2 GiB. Larger preservations will trigger undefined behaviour. While preservations larger than 2 GiB can't be obtained via folios currently, they can be obtained via kho_preserve_pages(). For example, memblock reserve_mem uses kho_preserve_pages(). Reservations larger than 2 GiB are valid and will trigger this bug if properly aligned. Fix it by using 1UL for shifting. Fixes: fc33e4b44b27 ("kexec: enable KHO support for memory preservation") Reported-by: Sashiko Cc: stable@vger.kernel.org Signed-off-by: Pratyush Yadav (Google) Link: https://patch.msgid.link/20260727150240.889555-1-pratyush@kernel.org Signed-off-by: Mike Rapoport (Microsoft) --- kernel/liveupdate/kexec_handover.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index 175c08a6e41e..6fad9152387a 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -501,7 +501,7 @@ static int __init kho_preserved_memory_reserve(phys_addr_t phys, struct page *page; u64 sz; - sz = 1 << (order + PAGE_SHIFT); + sz = 1UL << (order + PAGE_SHIFT); page = kho_get_preserved_page(phys, order); /* Reserve the memory preserved in KHO in memblock */