linux-kernel - Re: [PATCH stable v4.9 v2] arm64: entry: Place an SB sequence following an ERET instruction

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Message-ID: <647d771d-441b-39f9-809a-19335ef16036@gmail.com>
Date:   Thu, 13 Aug 2020 13:52:56 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>,
        Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Kristina Martsenko <kristina.martsenko@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Andrew Jones <drjones@...hat.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Fangrui Song <maskray@...gle.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <kvmarm@...ts.cs.columbia.edu>
Subject: Re: [PATCH stable v4.9 v2] arm64: entry: Place an SB sequence
 following an ERET instruction



On 8/7/2020 11:17 AM, Florian Fainelli wrote:
> 
> 
> On 8/7/2020 6:14 AM, Greg KH wrote:
>> On Thu, Aug 06, 2020 at 01:00:54PM -0700, Florian Fainelli wrote:
>>>
>>>
>>> On 7/20/2020 11:26 AM, Florian Fainelli wrote:
>>>> On 7/20/20 6:04 AM, Greg KH wrote:
>>>>> On Thu, Jul 09, 2020 at 12:50:23PM -0700, Florian Fainelli wrote:
>>>>>> From: Will Deacon <will.deacon@....com>
>>>>>>
>>>>>> commit 679db70801da9fda91d26caf13bf5b5ccc74e8e8 upstream
>>>>>>
>>>>>> Some CPUs can speculate past an ERET instruction and potentially perform
>>>>>> speculative accesses to memory before processing the exception return.
>>>>>> Since the register state is often controlled by a lower privilege level
>>>>>> at the point of an ERET, this could potentially be used as part of a
>>>>>> side-channel attack.
>>>>>>
>>>>>> This patch emits an SB sequence after each ERET so that speculation is
>>>>>> held up on exception return.
>>>>>>
>>>>>> Signed-off-by: Will Deacon <will.deacon@....com>
>>>>>> [florian: Adjust hyp-entry.S to account for the label
>>>>>>   added change to hyp/entry.S]
>>>>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>>>>> ---
>>>>>> Changes in v2:
>>>>>>
>>>>>> - added missing hunk in hyp/entry.S per Will's feedback
>>>>>
>>>>> What about 4.19.y and 4.14.y trees?  I can't take something for 4.9.y
>>>>> and then have a regression if someone moves to a newer release, right?
>>>>
>>>> Sure, send you candidates for 4.14 and 4.19.
>>>
>>> Greg, did you have a chance to queue those changes for 4.9, 4.14 and 4.19?
>>>
>>> https://lore.kernel.org/linux-arm-kernel/20200720182538.13304-1-f.fainelli@gmail.com/
>>> https://lore.kernel.org/linux-arm-kernel/20200720182937.14099-1-f.fainelli@gmail.com/
>>> https://lore.kernel.org/linux-arm-kernel/20200709195034.15185-1-f.fainelli@gmail.com/
>>
>> Nope, I was waiting for Will's "ack" for these.
> 
> OK, Will, can you review those? Thanks

Will, can you please review those patches?
-- 
Florian