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Message-ID: <CAGXu5jKcZope_h1Hr2iAwzOe16A=sT-UXJF2ugg2w8rV0_i7jA@mail.gmail.com>
Date: Tue, 22 May 2018 10:20:08 -0700
From: Kees Cook <keescook@...omium.org>
To: Alexander Popov <alex.popov@...ux.com>
Cc: Ingo Molnar <mingo@...nel.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>, Andy Lutomirski <luto@...nel.org>,
Tycho Andersen <tycho@...ho.ws>, Laura Abbott <labbott@...hat.com>, 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 v12 2/6] x86/entry: Add STACKLEAK erasing the kernel stack
at the end of syscalls
On Tue, May 22, 2018 at 3:58 AM, Alexander Popov <alex.popov@...ux.com> wrote:
> Hello Ingo and Kees,
>
> On 18.05.2018 09:53, Ingo Molnar wrote:
>> * Alexander Popov <alex.popov@...ux.com> wrote:
>>> --- a/arch/x86/kernel/process_32.c
>>> +++ b/arch/x86/kernel/process_32.c
>>> @@ -136,6 +136,11 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
>>> p->thread.sp0 = (unsigned long) (childregs+1);
>>> memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
>>>
>>> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
>>> + p->thread.lowest_stack.val = (unsigned long)end_of_stack(p) +
>>> + sizeof(unsigned long);
>>> +#endif
>>
>> This should use an inline helper:
>>
>> stackleak_task_init(p);
>
> Right now I can't define such a helper because 'lowest_stack' is a part of
> 'thread_struct', but arch/x86/include/asm/processor.h and include/linux/sched.h
> are independent.
>
> I think the best solution is to move 'lowest_stack' variable to 'task_struct'.
It might be possible work around this by using a macro in stackleak.h
(pardon any whitespace damage):
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
# define stackleak_task_init(task) do { \
task->thread.stack_leak.lowest_stack = \
(unsigned long)end_of_stack(task) + \
sizeof(unsigned long); \
} while (0)
#else
# define stackleak_task_init(task) do { } while (0)
#endif
> Is there any reason to fold this variable into a 'stackleak_info' structure? I
> see everybody happily uses #ifdef in 'task_struct'.
I'd rather it stay in threadinfo, but I could be convinced otherwise.
-Kees
--
Kees Cook
Pixel Security
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