linux-kernel - Re: [PATCH v4 5/7] kasan: allow kasan_check_read/write() to accept pointers to volatiles

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Date:   Mon, 19 Jun 2017 15:11:21 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v4 5/7] kasan: allow kasan_check_read/write() to accept
 pointers to volatiles

On Mon, Jun 19, 2017 at 12:50 PM, Mark Rutland <mark.rutland@....com> wrote:
> On Sat, Jun 17, 2017 at 11:15:31AM +0200, Dmitry Vyukov wrote:
>> Currently kasan_check_read/write() accept 'const void*', make them
>> accept 'const volatile void*'. This is required for instrumentation
>> of atomic operations and there is just no reason to not allow that.
>>
>> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: linux-kernel@...r.kernel.org
>> Cc: x86@...nel.org
>> Cc: linux-mm@...ck.org
>> Cc: kasan-dev@...glegroups.com
>
> Looks sane to me, and I can confirm this doesn't advervsely affect
> arm64. FWIW:
>
> Acked-by: Mark Rutland <mark.rutland@....com>
>
> Mark.


Great! Thanks for testing.

Ingo, what are your thoughts? Are you taking this to locking tree? When?



>> ---
>>  include/linux/kasan-checks.h | 10 ++++++----
>>  mm/kasan/kasan.c             |  4 ++--
>>  2 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/kasan-checks.h b/include/linux/kasan-checks.h
>> index b7f8aced7870..41960fecf783 100644
>> --- a/include/linux/kasan-checks.h
>> +++ b/include/linux/kasan-checks.h
>> @@ -2,11 +2,13 @@
>>  #define _LINUX_KASAN_CHECKS_H
>>
>>  #ifdef CONFIG_KASAN
>> -void kasan_check_read(const void *p, unsigned int size);
>> -void kasan_check_write(const void *p, unsigned int size);
>> +void kasan_check_read(const volatile void *p, unsigned int size);
>> +void kasan_check_write(const volatile void *p, unsigned int size);
>>  #else
>> -static inline void kasan_check_read(const void *p, unsigned int size) { }
>> -static inline void kasan_check_write(const void *p, unsigned int size) { }
>> +static inline void kasan_check_read(const volatile void *p, unsigned int size)
>> +{ }
>> +static inline void kasan_check_write(const volatile void *p, unsigned int size)
>> +{ }
>>  #endif
>>
>>  #endif
>> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
>> index c81549d5c833..edacd161c0e5 100644
>> --- a/mm/kasan/kasan.c
>> +++ b/mm/kasan/kasan.c
>> @@ -333,13 +333,13 @@ static void check_memory_region(unsigned long addr,
>>       check_memory_region_inline(addr, size, write, ret_ip);
>>  }
>>
>> -void kasan_check_read(const void *p, unsigned int size)
>> +void kasan_check_read(const volatile void *p, unsigned int size)
>>  {
>>       check_memory_region((unsigned long)p, size, false, _RET_IP_);
>>  }
>>  EXPORT_SYMBOL(kasan_check_read);
>>
>> -void kasan_check_write(const void *p, unsigned int size)
>> +void kasan_check_write(const volatile void *p, unsigned int size)
>>  {
>>       check_memory_region((unsigned long)p, size, true, _RET_IP_);
>>  }
>> --
>> 2.13.1.518.g3df882009-goog
>>