linux-kernel - Re: [PATCH v7 07/12] mm: slub: introduce metadata_access_enable()/metadata_access

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Date:	Tue, 25 Nov 2014 16:22:53 +0400
From:	Dmitry Chernenkov <dmitryc@...gle.com>
To:	Andrey Ryabinin <a.ryabinin@...sung.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Konstantin Serebryany <kcc@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Dave Jones <davej@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v7 07/12] mm: slub: introduce metadata_access_enable()/metadata_access_disable()

LGTM

Does this mean we're going to sanitize the slub code itself?)

On Mon, Nov 24, 2014 at 9:02 PM, Andrey Ryabinin <a.ryabinin@...sung.com> wrote:
> Wrap access to object's metadata in external functions with
> metadata_access_enable()/metadata_access_disable() function calls.
>
> This hooks separates payload accesses from metadata accesses
> which might be useful for different checkers (e.g. KASan).
>
> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
> ---
>  mm/slub.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 0c01584..88ad8b8 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -467,13 +467,23 @@ static int slub_debug;
>  static char *slub_debug_slabs;
>  static int disable_higher_order_debug;
>
> +static inline void metadata_access_enable(void)
> +{
> +}
> +
> +static inline void metadata_access_disable(void)
> +{
> +}
> +
>  /*
>   * Object debugging
>   */
>  static void print_section(char *text, u8 *addr, unsigned int length)
>  {
> +       metadata_access_enable();
>         print_hex_dump(KERN_ERR, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
>                         length, 1);
> +       metadata_access_disable();
>  }
>
>  static struct track *get_track(struct kmem_cache *s, void *object,
> @@ -503,7 +513,9 @@ static void set_track(struct kmem_cache *s, void *object,
>                 trace.max_entries = TRACK_ADDRS_COUNT;
>                 trace.entries = p->addrs;
>                 trace.skip = 3;
> +               metadata_access_enable();
>                 save_stack_trace(&trace);
> +               metadata_access_disable();
>
>                 /* See rant in lockdep.c */
>                 if (trace.nr_entries != 0 &&
> @@ -677,7 +689,9 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
>         u8 *fault;
>         u8 *end;
>
> +       metadata_access_enable();
>         fault = memchr_inv(start, value, bytes);
> +       metadata_access_disable();
>         if (!fault)
>                 return 1;
>
> @@ -770,7 +784,9 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
>         if (!remainder)
>                 return 1;
>
> +       metadata_access_enable();
>         fault = memchr_inv(end - remainder, POISON_INUSE, remainder);
> +       metadata_access_disable();
>         if (!fault)
>                 return 1;
>         while (end > fault && end[-1] == POISON_INUSE)
> --
> 2.1.3
>
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