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kho: fix size calculation in kho_preserved_memory_reserve()

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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: fc33e4b44b ("kexec: enable KHO support for memory preservation")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Link: https://patch.msgid.link/20260727150240.889555-1-pratyush@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
This commit is contained in:
Pratyush Yadav (Google) 2026-07-27 17:02:39 +02:00 committed by Mike Rapoport (Microsoft)
parent 5c4a03afcb
commit 3a0b8fa2eb
1 changed files with 1 additions and 1 deletions
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2
kernel/liveupdate/kexec_handover.c
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@ -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 */