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Fri, 07 Aug 2020 11:17:29 -0700 (PDT) Subject: Re: [PATCH stable v4.9 v2] arm64: entry: Place an SB sequence following an ERET instruction To: Greg KH , Will Deacon , Will Deacon Cc: linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org, Catalin Marinas , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Mark Rutland , Mark Brown , Kristina Martsenko , Sami Tolvanen , Andrew Jones , Ard Biesheuvel , Nick Desaulniers , Fangrui Song , open list , "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" References: <20200709195034.15185-1-f.fainelli@gmail.com> <20200720130411.GB494210@kroah.com> <9c29080e-8b3a-571c-3296-e0487fa473fa@gmail.com> <20200807131429.GB664450@kroah.com> From: Florian Fainelli Message-ID: Date: Fri, 7 Aug 2020 11:17:23 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Firefox/68.0 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200807131429.GB664450@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>>>> >>>>> 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 >>>>> [florian: Adjust hyp-entry.S to account for the label >>>>> added change to hyp/entry.S] >>>>> Signed-off-by: Florian Fainelli >>>>> --- >>>>> 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 -- Florian