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From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] mm/page_owner: track page free call chain
Date: Mon, 4 Jul 2016 14:29:55 +0900	[thread overview]
Message-ID: <20160704052955.GD14840@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <20160704050730.GC898@swordfish>

On Mon, Jul 04, 2016 at 02:07:30PM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> On (07/04/16 13:57), Joonsoo Kim wrote:
> > On Sun, Jul 03, 2016 at 01:16:56AM +0900, Sergey Senozhatsky wrote:
> > > Introduce PAGE_OWNER_TRACK_FREE config option to extend page owner with
> > > free_pages() tracking functionality. This adds to the dump_page_owner()
> > > output an additional backtrace, that tells us what path has freed the
> > > page.
> > 
> > Hmm... Do you have other ideas to use this feature? Following example is
> > just to detect use-after-free and we have other good tools for it
> > (KASAN or DEBUG_PAGEALLOC) so I'm not sure whether it's useful or not.
> 
> there is no kasan for ARM32, for example (apart from the fact that
> it's really hard to use kasan sometimes due to its cpu cycles and
> memory requirements).

Hmm... for debugging purpose, KASAN provides many more things so IMO it's
better to implement/support KASAN in ARM32 rather than expand
PAGE_OWNER for free.

> 
> educate me, will DEBUG_PAGEALLOC tell us what path has triggered the
> extra put_page()? hm... does ARM32 provide ARCH_SUPPORTS_DEBUG_PAGEALLOC?

Hmm... Now, I notice that PAGE_OWNER_TRACK_FREE will detect
double-free rather than use-after-free. DEBUG_PAGEALLOC doesn't catch
double-free but it can be implemented easily. In this case, we can
show call path for second free.

AFAIK, ARM32 doesn't support ARCH_SUPPORTS_DEBUG_PAGEALLOC.

Thanks.

WARNING: multiple messages have this Message-ID (diff)
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] mm/page_owner: track page free call chain
Date: Mon, 4 Jul 2016 14:29:55 +0900	[thread overview]
Message-ID: <20160704052955.GD14840@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <20160704050730.GC898@swordfish>

On Mon, Jul 04, 2016 at 02:07:30PM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> On (07/04/16 13:57), Joonsoo Kim wrote:
> > On Sun, Jul 03, 2016 at 01:16:56AM +0900, Sergey Senozhatsky wrote:
> > > Introduce PAGE_OWNER_TRACK_FREE config option to extend page owner with
> > > free_pages() tracking functionality. This adds to the dump_page_owner()
> > > output an additional backtrace, that tells us what path has freed the
> > > page.
> > 
> > Hmm... Do you have other ideas to use this feature? Following example is
> > just to detect use-after-free and we have other good tools for it
> > (KASAN or DEBUG_PAGEALLOC) so I'm not sure whether it's useful or not.
> 
> there is no kasan for ARM32, for example (apart from the fact that
> it's really hard to use kasan sometimes due to its cpu cycles and
> memory requirements).

Hmm... for debugging purpose, KASAN provides many more things so IMO it's
better to implement/support KASAN in ARM32 rather than expand
PAGE_OWNER for free.

> 
> educate me, will DEBUG_PAGEALLOC tell us what path has triggered the
> extra put_page()? hm... does ARM32 provide ARCH_SUPPORTS_DEBUG_PAGEALLOC?

Hmm... Now, I notice that PAGE_OWNER_TRACK_FREE will detect
double-free rather than use-after-free. DEBUG_PAGEALLOC doesn't catch
double-free but it can be implemented easily. In this case, we can
show call path for second free.

AFAIK, ARM32 doesn't support ARCH_SUPPORTS_DEBUG_PAGEALLOC.

Thanks.

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  reply	other threads:[~2016-07-04  5:26 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-02 16:16 [PATCH 0/3][RFC] mm/page:_owner: track page free call chain Sergey Senozhatsky
2016-07-02 16:16 ` Sergey Senozhatsky
2016-07-02 16:16 ` [PATCH 1/3] mm/page_owner: rename page_owner functions Sergey Senozhatsky
2016-07-02 16:16   ` Sergey Senozhatsky
2016-07-02 16:16 ` [PATCH 2/3] mm/page_owner: rename PAGE_EXT_OWNER flag Sergey Senozhatsky
2016-07-02 16:16   ` Sergey Senozhatsky
2016-07-02 16:16 ` [PATCH 3/3] mm/page_owner: track page free call chain Sergey Senozhatsky
2016-07-02 16:16   ` Sergey Senozhatsky
2016-07-03  5:59   ` Sergey Senozhatsky
2016-07-03  5:59     ` Sergey Senozhatsky
2016-07-04  4:57   ` Joonsoo Kim
2016-07-04  4:57     ` Joonsoo Kim
2016-07-04  5:07     ` Sergey Senozhatsky
2016-07-04  5:07       ` Sergey Senozhatsky
2016-07-04  5:29       ` Joonsoo Kim [this message]
2016-07-04  5:29         ` Joonsoo Kim
2016-07-04  5:45         ` Sergey Senozhatsky
2016-07-04  5:45           ` Sergey Senozhatsky
2016-07-04  7:29           ` Joonsoo Kim
2016-07-04  7:29             ` Joonsoo Kim
2016-07-04  7:53             ` Sergey Senozhatsky
2016-07-04  7:53               ` Sergey Senozhatsky
2016-07-08 12:11 [RFC][PATCH v2 " Sergey Senozhatsky
2016-07-11 14:27 ` [PATCH " Sergey Senozhatsky
2016-07-11 14:27   ` Sergey Senozhatsky

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