Re: [PATCH v4 11/36] arm64/mm: Map pages for guarded control stack
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2023-08-10 17:20:36
Also in:
kvmarm, linux-arch, linux-doc, linux-fsdevel, linux-kselftest, linux-mm, linux-riscv, lkml
On Mon, Aug 07, 2023 at 11:00:16PM +0100, Mark Brown wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 8f5b7ce857ed..8f40198cd44e 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c@@ -79,8 +79,18 @@ arch_initcall(adjust_protection_map); pgprot_t vm_get_page_prot(unsigned long vm_flags) { - pteval_t prot = pgprot_val(protection_map[vm_flags & + pteval_t prot; + + /* If this is a GCS then only interpret VM_WRITE. */ + if (system_supports_gcs() && (vm_flags & VM_SHADOW_STACK)) { + if (vm_flags & VM_WRITE) + prot = _PAGE_GCS; + else + prot = _PAGE_GCS_RO; + } else { + prot = pgprot_val(protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]); + } if (vm_flags & VM_ARM64_BTI) prot |= PTE_GP;
Some combinations here don't make sense like GCS + exec or BTI. I think the code above (correctly) ignores exec but it still sets PTE_GP if BTI (the architecture may allow this but you can't execute from the GCS page anyway). I haven't checked the x86 patches to see when VM_SHADOW_STACK is set but if there's no additional check at a higher level, we should add something to arch_validate_flags(), assuming it's called on those paths. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel