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

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Date: Thu, 27 Jun 2024 15:53:14 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Linus Walleij <linus.walleij@...aro.org>
CC: <linux@...linux.org.uk>, <ardb@...nel.org>, <arnd@...db.de>, <afd@...com>,
	<akpm@...ux-foundation.org>, <rmk+kernel@...linux.org.uk>,
	<eric.devolder@...cle.com>, <robh@...nel.org>, <kees@...nel.org>,
	<masahiroy@...nel.org>, <palmer@...osinc.com>, <samitolvanen@...gle.com>,
	<xiao.w.wang@...el.com>, <alexghiti@...osinc.com>, <nathan@...nel.org>,
	<jan.kiszka@...mens.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v2] ARM: Add support for STACKLEAK gcc plugin



On 2024/6/24 15:30, Linus Walleij wrote:
> On Mon, Jun 24, 2024 at 4:33 AM Jinjie Ruan <ruanjinjie@...wei.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@...wei.com>
>> Acked-by: Ard Biesheuvel <ardb@...nel.org>
> 
> Reviewed-by: Linus Walleij <linus.walleij@...aro.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