From 141d1497aae004808ecb156ca2bfb5e0bc460a2e Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 9 Mar 2017 21:52:06 +0100 Subject: [PATCH] arm64/mmu: add contiguous bit to sanity bug check A mapping with the contiguous bit cannot be safely manipulated while live, regardless of whether the bit changes between the old and new mapping. So take this into account when deciding whether the change is safe. Reviewed-by: Mark Rutland Tested-by: Mark Rutland Signed-off-by: Ard Biesheuvel Signed-off-by: Catalin Marinas --- arch/arm64/mm/mmu.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index ec23aec6433f..382ebd6ef46f 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -103,7 +103,15 @@ static bool pgattr_change_is_safe(u64 old, u64 new) */ static const pteval_t mask = PTE_PXN | PTE_RDONLY | PTE_WRITE; - return old == 0 || new == 0 || ((old ^ new) & ~mask) == 0; + /* creating or taking down mappings is always safe */ + if (old == 0 || new == 0) + return true; + + /* live contiguous mappings may not be manipulated at all */ + if ((old | new) & PTE_CONT) + return false; + + return ((old ^ new) & ~mask) == 0; } static void alloc_init_pte(pmd_t *pmd, unsigned long addr, -- 2.20.1