Re: [PATCH v2] ARM: Add support for STACKLEAK gcc plugin

[Jinjie Ruan <ruanjinjie@huawei.com>]

On 2024/6/24 15:30, Linus Walleij wrote:
> On Mon, Jun 24, 2024 at 4:33 AM Jinjie Ruan <ruanjinjie@huawei.com> 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@huawei.com>
>> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> 
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> 
> 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.
> 
Thank you very much, as Kees said, can this patch go via
rmk's patch tracker now?

> Yours,
> Linus Walleij