[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAGXu5j+2d-2SpzitAaB65zT6FjhmOYiCKSRfRQHcUUvOQ1CDGg@mail.gmail.com>
Date: Tue, 26 Jun 2018 17:13:58 -0700
From: Kees Cook <keescook@...omium.org>
To: Laura Abbott <labbott@...hat.com>
Cc: Alexander Popov <alex.popov@...ux.com>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>, Ingo Molnar <mingo@...nel.org>,
Andy Lutomirski <luto@...nel.org>, Tycho Andersen <tycho@...ho.ws>, Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, Borislav Petkov <bp@...en8.de>,
Richard Sandiford <richard.sandiford@....com>, Thomas Gleixner <tglx@...utronix.de>,
"H . Peter Anvin" <hpa@...or.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
"Dmitry V . Levin" <ldv@...linux.org>, Emese Revfy <re.emese@...il.com>, Jonathan Corbet <corbet@....net>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, Thomas Garnier <thgarnie@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>, Alexei Starovoitov <ast@...nel.org>, Josef Bacik <jbacik@...com>,
Masami Hiramatsu <mhiramat@...nel.org>, Nicholas Piggin <npiggin@...il.com>,
Al Viro <viro@...iv.linux.org.uk>, "David S . Miller" <davem@...emloft.net>,
Ding Tianhong <dingtianhong@...wei.com>, David Woodhouse <dwmw@...zon.co.uk>,
Josh Poimboeuf <jpoimboe@...hat.com>, Steven Rostedt <rostedt@...dmis.org>,
Dominik Brodowski <linux@...inikbrodowski.net>, Juergen Gross <jgross@...e.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Dan Williams <dan.j.williams@...el.com>,
Dave Hansen <dave.hansen@...ux.intel.com>, Mathias Krause <minipli@...glemail.com>,
Vikas Shivappa <vikas.shivappa@...ux.intel.com>, Kyle Huey <me@...ehuey.com>,
Dmitry Safonov <dsafonov@...tuozzo.com>, Will Deacon <will.deacon@....com>,
Arnd Bergmann <arnd@...db.de>, Florian Weimer <fweimer@...hat.com>,
Boris Lukashev <blukashev@...pervictus.com>, Andrey Konovalov <andreyknvl@...gle.com>,
X86 ML <x86@...nel.org>, LKML <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 Fri, Jun 22, 2018 at 11:58 AM, Laura Abbott <labbott@...hat.com> wrote:
> 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.
static inline unsigned long current_top_of_stack(void)
{
/*
* We can't read directly from tss.sp0: sp0 on x86_32 is special in
* and around vm86 mode and sp0 on x86_64 is special because of the
* entry trampoline.
*/
return this_cpu_read_stable(cpu_current_top_of_stack);
}
static inline bool on_thread_stack(void)
{
return (unsigned long)(current_top_of_stack() -
current_stack_pointer) < THREAD_SIZE;
}
The only arch-specific part is current_top_of_stack(), so it seems
like just solving current_top_of_stack() and copying on_thread_stack()
directly should work, yes? I would think sticking those directly into
asm/processor.h on arm64 would be okay?
FWIW, I don't think a separate asm/stackleak.h is needed.
-Kees
--
Kees Cook
Pixel Security
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
