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 11:50:08 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     peterz@...radead.org, mingo@...hat.com, will.deacon@....com,
        hpa@...or.com, aryabinin@...tuozzo.com, kasan-dev@...glegroups.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Subject: Re: [PATCH v4 5/7] kasan: allow kasan_check_read/write() to accept
 pointers to volatiles

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.

> ---
>  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
>