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Message-ID: <3e319e96-e942-7c87-7b72-a5c3f520f234@redhat.com>
Date: Fri, 22 Jun 2018 11:58:00 -0700
From: Laura Abbott <labbott@...hat.com>
To: Alexander Popov <alex.popov@...ux.com>,
kernel-hardening@...ts.openwall.com, Kees Cook <keescook@...omium.org>,
PaX Team <pageexec@...email.hu>, Brad Spengler <spender@...ecurity.net>,
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Andrey Konovalov <andreyknvl@...gle.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 (resend) 2/6] x86/entry: Add STACKLEAK erasing the
kernel stack at the end of syscalls
On 06/22/2018 09:58 AM, Alexander Popov wrote:
> + /*
> + * Now write the poison value to the kernel stack. Start from
> + * 'kstack_ptr' and move up till the new 'boundary'. We assume that
> + * the stack pointer doesn't change when we write poison.
> + */
> + if (on_thread_stack())
> + boundary = current_stack_pointer;
> + else
> + boundary = current_top_of_stack();
> +
> + BUG_ON(boundary - kstack_ptr >= THREAD_SIZE);
> +
> + while (kstack_ptr < boundary) {
> + *(unsigned long *)kstack_ptr = STACKLEAK_POISON;
> + kstack_ptr += sizeof(unsigned long);
> + }
> +
> + /* Reset the 'lowest_stack' value for the next syscall */
> + current->lowest_stack = current_top_of_stack() - THREAD_SIZE / 64;
on_thread_stack() and current_top_of_stack() are x86 only
functions currently defined in asm/processor.h. There are
similar functions in arch/arm64/include/asm/stacktrace.h
which I think I can use to build those functions. Should
I just throw the arm64 versions in processor.h or do
we want to consider abstracting these into something like
asm/stackleak.h? I'd like to know a direction before I
start ripping apart stacktrace.h.
Thanks,
Laura
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