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From: Vlastimil Babka <vbabka@suse.cz>
To: Walter Wu <walter-zh.wu@mediatek.com>
Cc: Qian Cai <cai@lca.pw>, Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Alexander Potapenko <glider@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com
Subject: Re: [PATCH v3] mm/kasan: dump alloc and free stack for page allocator
Date: Thu, 12 Sep 2019 16:31:42 +0200
Message-ID: <613f9f23-c7f0-871f-fe13-930c35ef3105@suse.cz> (raw)
In-Reply-To: <1568297308.19040.5.camel@mtksdccf07>

On 9/12/19 4:08 PM, Walter Wu wrote:
> 
>>   extern void __reset_page_owner(struct page *page, unsigned int order);
>> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
>> index 6c9682ce0254..dc560c7562e8 100644
>> --- a/lib/Kconfig.kasan
>> +++ b/lib/Kconfig.kasan
>> @@ -41,6 +41,8 @@ config KASAN_GENERIC
>>   	select SLUB_DEBUG if SLUB
>>   	select CONSTRUCTORS
>>   	select STACKDEPOT
>> +	select PAGE_OWNER
>> +	select PAGE_OWNER_FREE_STACK
>>   	help
>>   	  Enables generic KASAN mode.
>>   	  Supported in both GCC and Clang. With GCC it requires version 4.9.2
>> @@ -63,6 +65,8 @@ config KASAN_SW_TAGS
>>   	select SLUB_DEBUG if SLUB
>>   	select CONSTRUCTORS
>>   	select STACKDEPOT
>> +	select PAGE_OWNER
>> +	select PAGE_OWNER_FREE_STACK
>>   	help
> 
> What is the difference between PAGE_OWNER+PAGE_OWNER_FREE_STACK and
> DEBUG_PAGEALLOC?

Same memory usage, but debug_pagealloc means also extra checks and 
restricting memory access to freed pages to catch UAF.

> If you directly enable PAGE_OWNER+PAGE_OWNER_FREE_STACK
> PAGE_OWNER_FREE_STACK,don't you think low-memory device to want to use
> KASAN?

OK, so it should be optional? But I think it's enough to distinguish no 
PAGE_OWNER at all, and PAGE_OWNER+PAGE_OWNER_FREE_STACK together - I 
don't see much point in PAGE_OWNER only for this kind of debugging.

So how about this? KASAN wouldn't select PAGE_OWNER* but it would be 
recommended in the help+docs. When PAGE_OWNER and KASAN are selected by 
user, PAGE_OWNER_FREE_STACK gets also selected, and both will be also 
runtime enabled without explicit page_owner=on.
I mostly want to avoid another boot-time option for enabling 
PAGE_OWNER_FREE_STACK.
Would that be enough flexibility for low-memory devices vs full-fledged 
debugging?


  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11  8:39 Walter Wu
2019-09-11 15:19 ` Qian Cai
2019-09-12 13:53   ` Vlastimil Babka
2019-09-12 14:08     ` Andrey Ryabinin
2019-09-12 14:08     ` Walter Wu
2019-09-12 14:31       ` Vlastimil Babka [this message]
2019-09-12 15:13         ` Walter Wu
2019-09-12 17:05         ` Andrey Ryabinin
2019-09-16  9:42           ` Vlastimil Babka
2019-09-16 15:57             ` Andrey Ryabinin
2019-09-17  8:19               ` Vlastimil Babka
2019-09-23  8:20               ` [PATCH] mm, debug, kasan: save and dump freeing stack trace for kasan Vlastimil Babka
2019-09-25  9:41                 ` Andrey Ryabinin
2019-09-12 14:10     ` [PATCH v3] mm/kasan: dump alloc and free stack for page allocator Qian Cai

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