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Thu, 06 Aug 2020 13:00:59 -0700 (PDT) Subject: Re: [PATCH stable v4.9 v2] arm64: entry: Place an SB sequence following an ERET instruction From: Florian Fainelli 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> Message-ID: <9c29080e-8b3a-571c-3296-e0487fa473fa@gmail.com> Date: Thu, 6 Aug 2020 13:00:54 -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: 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 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/ Thanks -- Florian