From: Andrey Konovalov <andreyknvl@google.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@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>,
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>,
linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-sparse@vger.kernel.org,
Linux Memory Management List <linux-mm@kvack.org>,
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Chintan Pandya <cpandya@codeaurora.org>,
Jacob Bramley <Jacob.Bramley@arm.com>,
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 00/17] khwasan: kernel hardware assisted address sanitizer
Date: Thu, 28 Jun 2018 20:56:41 +0200 [thread overview]
Message-ID: <CAAeHK+w0T43+h3xqU4a-qutxd-qiEhsvk0eaZpmAn-T0hpaLZQ@mail.gmail.com> (raw)
In-Reply-To: <20180628105057.GA26019@e103592.cambridge.arm.com>
On Thu, Jun 28, 2018 at 12:51 PM, Dave Martin <Dave.Martin@arm.com> wrote:
> On Tue, Jun 26, 2018 at 03:15:10PM +0200, Andrey Konovalov wrote:
>> 1. By using the Top Byte Ignore arm64 CPU feature, we can store pointer
>> tags in the top byte of each kernel pointer.
>
> [...]
>
> This is a change from the current situation, so the kernel may be
> making implicit assumptions about the top byte of kernel addresses.
>
> Randomising the top bits may cause things like address conversions and
> pointer arithmetic to break.
>
> For example, (q - p) will not produce the expected result if q and p
> have different tags.
If q and p have different tags, that means they come from different
allocations. I don't think it would make sense to calculate pointer
difference in this case.
>
> Conversions, such as between pointer and pfn, may also go wrong if not
> appropriately masked.
>
> There are also potential pointer comparison and aliasing issues if
> the tag bits are ever stripped or modified.
>
>
> What was your approach to tracking down all the points in the code
> where we have a potential issue?
I've been fuzzing the kernel built with KWHASAN with syzkaller. This
gives a decent coverage and I was able to find some places where
fixups were required this way. Right now the fuzzer is running without
issues. It doesn't prove that all such places are fixed, but I don't
know a better way to test this.
next prev parent reply other threads:[~2018-06-28 18:56 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
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 [this message]
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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