linux-kernel - Re: [PATCH v3] kprobes: unpoison stack in jprobe

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Date:   Fri, 14 Oct 2016 13:55:26 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Will Deacon <will.deacon@....com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Eugene Surovegin <surovegin@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Alexander Potapenko <glider@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH v3] kprobes: unpoison stack in jprobe_return() for KASAN

On Fri, Oct 14, 2016 at 1:25 PM, Will Deacon <will.deacon@....com> wrote:
> On Fri, Oct 14, 2016 at 12:53:56PM +0200, Dmitry Vyukov wrote:
>> KASAN stack instrumentation poisons stack redzones on function entry
>> and unpoisons them on function exit. If a function exits abnormally
>> (e.g. with a longjmp like jprobe_return()), stack redzones are left
>> poisoned. Later this leads to random KASAN false reports.
>>
>> Unpoison stack redzones in the frames we are going to jump over
>> before doing actual longjmp in jprobe_return().
>>
>> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>> Cc: Alexander Potapenko <glider@...gle.com>
>> Cc: Will Deacon <will.deacon@....com>
>> Cc: Ingo Molnar <mingo@...nel.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
>> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
>> Cc: "David S. Miller" <davem@...emloft.net>
>> Cc: Masami Hiramatsu <mhiramat@...nel.org>
>> Cc: x86@...nel.org
>> Cc: kasan-dev@...glegroups.com
>>
>> --
>>
>> Changes since v1:
>>  - leave kasan_unpoison_remaining_stack() intact
>>  - instead add kasan_unpoison_stack_above_sp_to()
>>  - rename kasan_unpoison_remaining_stack() to kasan_unpoison_task_stack_below()
>>
>> Changes since v2:
>>  - fix build by adding return type to kasan_unpoison_stack_above_sp_to
>>    (tested v2 with it, but forgot to git add)
>
> I get build warnings with this patch applied and KASAN enabled:
>
> mm/kasan/kasan.c: In function ‘kasan_unpoison_task_stack_below’:
> mm/kasan/kasan.c:82:34: warning: passing argument 2 of ‘__kasan_unpoison_stack’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
>   __kasan_unpoison_stack(current, watermark);
>                                   ^~~~~~~~~
> mm/kasan/kasan.c:65:13: note: expected ‘void *’ but argument is of type ‘const void *’
>  static void __kasan_unpoison_stack(struct task_struct *task, void *sp)
>              ^~~~~~~~~~~~~~~~~~~~~~
> mm/kasan/kasan.c: In function ‘kasan_unpoison_stack_above_sp_to’:
> mm/kasan/kasan.c:92:27: error: called object ‘current_stack_pointer’ is not a function or function pointer
>   const void *sp = (void *)current_stack_pointer();
>                            ^~~~~~~~~~~~~~~~~~~~~


Mailed v4.

Thanks