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

[Florian Fainelli]

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@xxxxxxx>
> > > > > >
> > > > > > 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@xxxxxxx>
> > > > > > [florian: Adjust hyp-entry.S to account for the label
> > > > > >   added change to hyp/entry.S]
> > > > > > Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> > > > > > ---
> > > > > > 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@xxxxxxxxx/
> > > https://lore.kernel.org/linux-arm-kernel/20200720182937.14099-1-f.fainelli@xxxxxxxxx/
> > > https://lore.kernel.org/linux-arm-kernel/20200709195034.15185-1-f.fainelli@xxxxxxxxx/
> >
> > 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