From: Robin Murphy <robin.murphy@arm.com>
To: Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
kernel-team@android.com, Michael Ellerman <mpe@ellerman.id.au>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Segher Boessenkool <segher@kernel.crashing.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Arnd Bergmann <arnd@arndb.de>,
Peter Oberparleiter <oberpar@linux.ibm.com>,
Masahiro Yamada <masahiroy@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH v4 05/11] arm64: csum: Disable KASAN for do_csum()
Date: Wed, 22 Apr 2020 12:01:53 +0100 [thread overview]
Message-ID: <6efa0cc1-bd3e-b9b6-4e69-7ac05e6efe35@arm.com> (raw)
In-Reply-To: <20200422104138.GA30265@willie-the-truck>
On 2020-04-22 11:41 am, Will Deacon wrote:
> On Wed, Apr 22, 2020 at 10:49:52AM +0100, Mark Rutland wrote:
>> On Tue, Apr 21, 2020 at 04:15:31PM +0100, Will Deacon wrote:
>>> do_csum() over-reads the source buffer and therefore abuses
>>> READ_ONCE_NOCHECK() to avoid tripping up KASAN. In preparation for
>>> READ_ONCE_NOCHECK() becoming a macro, and therefore losing its
>>> '__no_sanitize_address' annotation, just annotate do_csum() explicitly
>>> and fall back to normal loads.
>>>
>>> Cc: Mark Rutland <mark.rutland@arm.com>
>>> Cc: Robin Murphy <robin.murphy@arm.com>
>>> Signed-off-by: Will Deacon <will@kernel.org>
>>
>> From a functional perspective:
>>
>> Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> Thanks.
>
>> I know that Robin had a concern w.r.t. how this would affect the
>> codegen, but I think we can follow that up after the series as a whole
>> is merged.
>
> Makes sense. I did look at the codegen, fwiw, and it didn't seem especially
> bad. One of the LDP's gets cracked in the unlikely() path, but it didn't
> look like it would be a disaster (and sprinkling barrier() around to force
> the LDP felt really fragile!).
Sure - I have a nagging feeling that it could still do better WRT
pipelining the loads anyway, so I'm happy to come back and reconsider
the local codegen later. It certainly doesn't deserve to stand in the
way of cross-arch rework.
Other than dereferencing the ptr argument, this code has no cause to
make any explicit memory accesses of its own, so I don't think we lose
any practical KASAN coverage by moving the annotation to function level.
Given all that,
Acked-by: Robin Murphy <robin.murphy@arm.com>
Cheers,
Robin.
next prev parent reply other threads:[~2020-04-22 11:01 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 15:15 [PATCH v4 00/11] Rework READ_ONCE() to improve codegen Will Deacon
2020-04-21 15:15 ` [PATCH v4 01/11] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8 Will Deacon
2020-04-21 17:15 ` Masahiro Yamada
2020-04-21 15:15 ` [PATCH v4 02/11] netfilter: Avoid assigning 'const' pointer to non-const pointer Will Deacon
2020-04-21 15:15 ` [PATCH v4 03/11] net: tls: " Will Deacon
2020-04-21 15:15 ` [PATCH v4 04/11] fault_inject: Don't rely on "return value" from WRITE_ONCE() Will Deacon
2020-04-21 15:15 ` [PATCH v4 05/11] arm64: csum: Disable KASAN for do_csum() Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-22 9:49 ` Mark Rutland
2020-04-22 9:49 ` Mark Rutland
2020-04-22 10:41 ` Will Deacon
2020-04-22 11:01 ` Robin Murphy [this message]
2020-04-24 9:41 ` David Laight
2020-04-24 11:00 ` Robin Murphy
2020-04-24 13:04 ` David Laight
2020-04-24 13:04 ` David Laight
2020-04-21 15:15 ` [PATCH v4 06/11] READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE() Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-22 9:51 ` Mark Rutland
2020-04-21 15:15 ` [PATCH v4 07/11] READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-24 16:31 ` Jann Horn
2020-04-24 17:11 ` Will Deacon
2020-04-24 17:43 ` Peter Zijlstra
2020-04-21 15:15 ` [PATCH v4 08/11] READ_ONCE: Drop pointer qualifiers when reading from scalar types Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-22 10:25 ` Rasmus Villemoes
2020-04-22 11:48 ` Segher Boessenkool
2020-04-22 11:48 ` Segher Boessenkool
2020-04-22 13:11 ` Will Deacon
2020-04-22 13:11 ` Will Deacon
2020-04-22 14:54 ` Will Deacon
2020-04-21 15:15 ` [PATCH v4 09/11] locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-21 15:15 ` [PATCH v4 10/11] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros Will Deacon
2020-04-21 15:15 ` [PATCH v4 11/11] gcov: Remove old GCC 3.4 support Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-21 17:19 ` Masahiro Yamada
2020-04-21 18:42 ` [PATCH v4 00/11] Rework READ_ONCE() to improve codegen Linus Torvalds
2020-04-21 18:42 ` Linus Torvalds
2020-04-22 8:18 ` Will Deacon
2020-04-22 11:37 ` Peter Zijlstra
2020-04-22 12:26 ` Will Deacon
2020-04-24 13:42 ` Will Deacon
2020-04-24 15:54 ` Marco Elver
2020-04-24 16:52 ` Will Deacon
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