[PATCH stable 4.9] arm64: entry: Place an SB sequence following an ERET instruction

[Florian Fainelli]

On 6/11/20 9:42 PM, Florian Fainelli wrote:
> From: Will Deacon <will.deacon at 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 at arm.com>
> [florian: Adjust hyp-entry.S to account for the label]
> Signed-off-by: Florian Fainelli <f.fainelli at gmail.com>
> ---
> Will,
> 
> Can you confirm that for 4.9 these are the only places that require
> patching? Thank you!

Hi Will, Catalin,

Does this look good to you for a 4.9 backport? I would like to see this
included at some point since this pertains to CVE-2020-13844.

Thanks!
-- 
Florian