From: "Pratyush Yadav (Google)" 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") Cc: stable@vger.kernel.org Signed-off-by: Pratyush Yadav (Google) --- Stable backport note: This patch fixes kho_preserved_memory_reserve(), which was added by 3f2ad90060f6 ("kho: adopt radix tree for preserved memory tracking") in v7.1. The bug in older kernels was in deserialize_bitmap(), which was added by fc33e4b44b27 ("kexec: enable KHO support for memory preservation") in v6.16. --- 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 */ base-commit: 5c4a03afcb21783987ffc64562b76ddd5a21b12b -- 2.55.0.229.g6434b31f56-goog