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

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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



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