[kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only

On 13 February 2016 at 01:31, David Brown [off-list ref] wrote:

On Thu, Feb 11, 2016 at 03:19:20PM +0100, Ard Biesheuvel wrote:

quoted

quoted

diff --git a/arch/arm64/kernel/vdso/vdso.S

b/arch/arm64/kernel/vdso/vdso.S
index 60c1db5..db7c0f2 100644

--- a/arch/arm64/kernel/vdso/vdso.S
+++ b/arch/arm64/kernel/vdso/vdso.S

@@ -24,6 +24,7 @@
        __PAGE_ALIGNED_DATA

^^ You can get rid of this now as well

Can we?  The page is getting mapped to userspace, and if we didn't
page align it, we could leak kernel read-only data to every userspace
process.

That's what the .balign is for. __PAGE_ALIGNED_DATA only sets the
section, and you're overriding that right after.