From: Richard Cheng Date: Tue, 21 Jul 2026 10:00:26 +0000 (+0800) Subject: arm64/mm: Check the requested PFN range during memory removal X-Git-Tag: v7.2-rc5~23^2~1 X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=285f90a4d1141c7594f2368e19cbb307388eff30;p=thirdparty%2Fkernel%2Flinux.git arm64/mm: Check the requested PFN range during memory removal prevent_memory_remove_notifier() advances pfn while scanning the requested range for early memory. When the loop completes, pfn is at or beyond end_pfn. Passing it to can_unmap_without_split() therefore checks a range after the one being offlined. Consequently, a valid request can be rejected based on the following range, while a request that would split a leaf mapping can be accepted if the shifted range can be unmapped without a split. This was observed with CXL DAX memory, where the final memory block was incorrectly allowed to be offlined. Pass arg->start_pfn into can_unmap_without_split() so it checks the requested range. Fixes: 95a58852b0e5 ("arm64/mm: Reject memory removal that splits a kernel leaf mapping") Signed-off-by: Richard Cheng Reviewed-by: Anshuman Khandual Signed-off-by: Will Deacon --- diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index a25d8beacc83..18a8b0d3714e 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -2194,7 +2194,7 @@ static int prevent_memory_remove_notifier(struct notifier_block *nb, } } - if (!can_unmap_without_split(pfn, arg->nr_pages)) + if (!can_unmap_without_split(arg->start_pfn, arg->nr_pages)) return NOTIFY_BAD; return NOTIFY_OK;