From: Dmitry Vyukov <dvyukov@google.com>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
vincenzo.frascino@arm.com,
Alexander Potapenko <glider@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mark Rutland <mark.rutland@arm.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Marc Zyngier <marc.zyngier@arm.com>,
Dave Martin <dave.martin@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Ingo Molnar <mingo@kernel.org>,
Paul Lawrence <paullawrence@google.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Arnd Bergmann <arnd@arndb.de>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kate Stewart <kstewart@linuxfoundation.org>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
kasan-dev <kasan-dev@googlegroups.com>,
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Chintan Pandya <cpandya@codeaurora.org>,
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Jann Horn <jannh@google.com>,
Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
Lee Smith <Lee.Smith@arm.com>, Kostya Serebryany <kcc@google.com>,
Mark Brand <markbrand@google.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
Evgeniy Stepanov <eugenis@google.com>
Subject: Re: [PATCH v4 13/17] khwasan: add hooks implementation
Date: Tue, 31 Jul 2018 17:03:48 +0200 [thread overview]
Message-ID: <CACT4Y+Y=61VwwETQP3FwAN16ompSNJOCyDCG6Ew1Bm5f_Fe1Lw@mail.gmail.com> (raw)
In-Reply-To: <8240d4f9-c8df-cfe9-119d-6e933f8b13df@virtuozzo.com>
On Tue, Jul 31, 2018 at 4:50 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
>
> On 07/31/2018 04:05 PM, Andrey Konovalov wrote:
>> On Wed, Jul 25, 2018 at 3:44 PM, Vincenzo Frascino@Foss
>> <vincenzo.frascino@arm.com> wrote:
>>> On 06/26/2018 02:15 PM, Andrey Konovalov wrote:
>>>
>>>> @@ -325,18 +341,41 @@ void kasan_init_slab_obj(struct kmem_cache *cache,
>>>> const void *object)
>>>> void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t
>>>> flags)
>>>> {
>>>> - return kasan_kmalloc(cache, object, cache->object_size, flags);
>>>> + object = kasan_kmalloc(cache, object, cache->object_size, flags);
>>>> + if (IS_ENABLED(CONFIG_KASAN_HW) && unlikely(cache->ctor)) {
>>>> + /*
>>>> + * Cache constructor might use object's pointer value to
>>>> + * initialize some of its fields.
>>>> + */
>>>> + cache->ctor(object);
>>>>
>>> This seams breaking the kmem_cache_create() contract: "The @ctor is run when
>>> new pages are allocated by the cache."
>>> (https://elixir.bootlin.com/linux/v3.7/source/mm/slab_common.c#L83)
>>>
>>> Since there might be preexisting code relying on it, this could lead to
>>> global side effects. Did you verify that this is not the case?
>>>
>>> Another concern is performance related if we consider this solution suitable
>>> for "near-production", since with the current implementation you call the
>>> ctor (where present) on an object multiple times and this ends up memsetting
>>> and repopulating the memory every time (i.e. inode.c: inode_init_once). Do
>>> you know what is the performance impact?
>>
>> We can assign tags to objects with constructors when a slab is
>> allocated and call constructors once as usual. The downside is that
>> such object would always have the same tag when it is reallocated, so
>> we won't catch use-after-frees.
>
> Actually you should do this for SLAB_TYPESAFE_BY_RCU slabs. Usually they are with ->ctors but there
> are few without constructors.
> We can't reinitialize or even retag them. The latter will definitely cause false-positive use-after-free reports.
Somewhat offtopic, but I can't understand how SLAB_TYPESAFE_BY_RCU
slabs can be useful without ctors or at least memset(0). Objects in
such slabs need to be type-stable, but I can't understand how it's
possible to establish type stability without a ctor... Are these bugs?
Or I am missing something subtle? What would be a canonical usage of
SLAB_TYPESAFE_BY_RCU slab without a ctor?
next prev parent reply other threads:[~2018-07-31 15:04 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-26 13:15 [PATCH v4 00/17] khwasan: kernel hardware assisted address sanitizer Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 01/17] khwasan, mm: change kasan hooks signatures Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 02/17] khwasan: move common kasan and khwasan code to common.c Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 03/17] khwasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_HW Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 04/17] khwasan, arm64: adjust shadow size for CONFIG_KASAN_HW Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 05/17] khwasan: initialize shadow to 0xff Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 06/17] khwasan, arm64: untag virt address in __kimg_to_phys and _virt_addr_is_linear Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 07/17] khwasan: add tag related helper functions Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 08/17] khwasan, arm64: fix up fault handling logic Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 09/17] khwasan, arm64: enable top byte ignore for the kernel Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 10/17] khwasan, mm: perform untagged pointers comparison in krealloc Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 11/17] khwasan: split out kasan_report.c from report.c Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 12/17] khwasan: add bug reporting routines Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 13/17] khwasan: add hooks implementation Andrey Konovalov
2018-07-25 13:44 ` Vincenzo Frascino@Foss
2018-07-31 13:05 ` Andrey Konovalov
2018-07-31 14:50 ` Andrey Ryabinin
2018-07-31 15:03 ` Dmitry Vyukov [this message]
2018-07-31 15:38 ` Christopher Lameter
2018-07-31 16:03 ` Dmitry Vyukov
2018-07-31 16:04 ` Andrey Ryabinin
2018-07-31 16:08 ` Dmitry Vyukov
2018-07-31 16:18 ` Andrey Ryabinin
2018-07-31 15:21 ` Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 14/17] khwasan, arm64: add brk handler for inline instrumentation Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 15/17] khwasan, mm, arm64: tag non slab memory allocated via pagealloc Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 16/17] khwasan: update kasan documentation Andrey Konovalov
2018-06-26 13:15 ` [PATCH v4 17/17] kasan: add SPDX-License-Identifier mark to source files Andrey Konovalov
2018-06-27 23:08 ` [PATCH v4 00/17] khwasan: kernel hardware assisted address sanitizer Andrew Morton
2018-06-28 0:04 ` Kostya Serebryany
[not found] ` <CAEZpscCcP6=O_OCqSwW8Y6u9Ee99SzWN+hRcgpP2tK=OEBFnNw@mail.gmail.com>
2018-06-28 1:11 ` Andrew Morton
2018-06-28 18:26 ` Andrey Konovalov
2018-06-28 7:01 ` Geert Uytterhoeven
2018-07-02 20:33 ` Matthew Wilcox
2018-07-02 23:39 ` Evgenii Stepanov
2018-06-28 18:29 ` Andrey Konovalov
2018-06-28 19:40 ` Andrew Morton
2018-06-29 12:45 ` Andrey Konovalov
2018-06-29 13:01 ` Mark Rutland
2018-06-29 14:40 ` Andrey Konovalov
2018-06-30 2:41 ` Andrew Morton
2018-07-02 19:16 ` Evgenii Stepanov
2018-07-02 19:21 ` Andrew Morton
2018-07-02 20:22 ` Evgenii Stepanov
2018-07-02 20:30 ` Andrew Morton
2018-06-28 10:51 ` Dave Martin
2018-06-28 18:56 ` Andrey Konovalov
2018-06-29 10:14 ` Mark Rutland
2018-06-29 11:04 ` Dave Martin
2018-06-29 11:26 ` Luc Van Oostenryck
2018-06-29 13:18 ` Andrey Konovalov
2018-06-29 13:42 ` Dan Carpenter
2018-06-29 11:07 ` Catalin Marinas
2018-06-29 11:07 ` Will Deacon
2018-06-29 16:36 ` Andrey Konovalov
2018-07-03 17:36 ` Will Deacon
2018-07-18 17:16 ` Andrey Konovalov
2018-07-31 13:22 ` Andrey Konovalov
2018-08-01 16:35 ` Will Deacon
2018-08-01 16:52 ` Dmitry Vyukov
2018-08-02 11:10 ` Catalin Marinas
2018-08-02 11:36 ` Dmitry Vyukov
2018-08-02 13:52 ` Catalin Marinas
2018-08-02 14:11 ` Andrey Ryabinin
2018-08-03 9:23 ` Will Deacon
2018-08-03 9:42 ` Dmitry Vyukov
2018-08-08 16:27 ` Will Deacon
2018-08-08 16:53 ` Dmitry Vyukov
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