Re: [PATCH v2] ARM: Add support for STACKLEAK gcc plugin
From: Linus Walleij
Date: Mon Jun 24 2024 - 03:30:23 EST
On Mon, Jun 24, 2024 at 4:33 AM Jinjie Ruan <ruanjinjie@xxxxxxxxxx> wrote:
> Add the STACKLEAK gcc plugin to arm32 by adding the helper used by
> stackleak common code: on_thread_stack(). It initialize the stack with the
> poison value before returning from system calls which improves the kernel
> security. Additionally, this disables the plugin in EFI stub code and
> decompress code, which are out of scope for the protection.
>
> Before the test on Qemu versatilepb board:
> # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT
> lkdtm: Performing direct entry STACKLEAK_ERASING
> lkdtm: XFAIL: stackleak is not supported on this arch (HAVE_ARCH_STACKLEAK=n)
>
> After:
> # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT
> lkdtm: Performing direct entry STACKLEAK_ERASING
> lkdtm: stackleak stack usage:
> high offset: 80 bytes
> current: 280 bytes
> lowest: 696 bytes
> tracked: 696 bytes
> untracked: 192 bytes
> poisoned: 7220 bytes
> low offset: 4 bytes
> lkdtm: OK: the rest of the thread stack is properly erased
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
> Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
I was digging around to see if this would interfere with BPF
trampolines, but the
BPF code seems so generic that I assume it already takes stackleak into account.
Yours,
Linus Walleij