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Message-ID: <23369d86-ad31-e7c5-e42f-28e0e51ec128@linux.com>
Date: Tue, 22 May 2018 13:58:59 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: Ingo Molnar <mingo@...nel.org>, Kees Cook <keescook@...omium.org>
Cc: kernel-hardening@...ts.openwall.com, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>, Andy Lutomirski <luto@...nel.org>,
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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>,
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"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
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<me@...ehuey.com>, Dmitry Safonov <dsafonov@...tuozzo.com>,
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Boris Lukashev <blukashev@...pervictus.com>,
Andrey Konovalov <andreyknvl@...gle.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 2/6] x86/entry: Add STACKLEAK erasing the kernel stack
at the end of syscalls
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'.
Is there any reason to fold this variable into a 'stackleak_info' structure? I
see everybody happily uses #ifdef in 'task_struct'.
May I define STACKLEAK_POISON and STACKLEAK_POISON_CHECK_DEPTH in sched.h as well?
Looking forward to your reply.
Best regards,
Alexander
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