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    SubjectRe: [PATCH stable v4.9 v2] arm64: entry: Place an SB sequence following an ERET instruction
    On Thu, Jul 09, 2020 at 12:50:23PM -0700, Florian Fainelli wrote:
    > From: Will Deacon <will.deacon@arm.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@arm.com>
    > [florian: Adjust hyp-entry.S to account for the label
    > added change to hyp/entry.S]
    > Signed-off-by: Florian Fainelli <f.fainelli@gmail.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?

    thanks,

    greg k-h

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