From cc5d2b3b95cdbb3fed4e38e667d17b9ac7250f7a Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 23 Nov 2015 13:26:19 +0000 Subject: [PATCH] arm64: mm: detect bad __create_mapping uses If a caller of __create_mapping provides a PA and VA which have different sub-page offsets, it is not clear which offset they expect to apply to the mapping, and is indicative of a bad caller. In some cases, the region we wish to map may validly have a sub-page offset in the physical and virtual addresses. For example, EFI runtime regions have 4K granularity, yet may be mapped by a 64K page kernel. So long as the physical and virtual offsets are the same, the region will be mapped at the expected VAs. Disallow calls with differing sub-page offsets, and WARN when they are encountered, so that we can detect and fix such cases. Cc: Laura Abbott Acked-by: Ard Biesheuvel Acked-by: Catalin Marinas Reviewed-by: Steve Capper Signed-off-by: Mark Rutland Signed-off-by: Will Deacon --- arch/arm64/mm/mmu.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 873e363048c6..6e4b4351ce9e 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -251,6 +251,13 @@ static void __create_mapping(struct mm_struct *mm, pgd_t *pgd, { unsigned long addr, length, end, next; + /* + * If the virtual and physical address don't have the same offset + * within a page, we cannot map the region as the caller expects. + */ + if (WARN_ON((phys ^ virt) & ~PAGE_MASK)) + return; + addr = virt & PAGE_MASK; length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));