APPLIED[F/Unstable]: [PATCH 0/1][SRU][E/F] PAN is broken for execute-only user mappings on ARMv8

[Seth Forshee]

On Wed, Jan 08, 2020 at 05:20:58PM +0000, Tyler Hicks wrote:
> BugLink: https://launchpad.net/bugs/1858815
> 
> Clean cherry-pick that is only build tested at this time. I'm relying on
> our SRU tests for regression testing.
> 
> [Impact]
> 
> It was discovered that upstream kernel commit cab15ce604e5 ("arm64:
> Introduce execute-only page access permissions"), which introduced
> execute-only user mappings, subverted the Privileged Access Never
> protections.
> 
> The fix is to effectively revert commit cab15ce604e5. This is done in
> upstream kernel commit 24cecc377463 ("arm64: Revert support for
> execute-only user mappings").
> 
> [Test Case]
> 
> I'm not aware of any PAN test cases. Booting our arm64 kernels on an
> ARMv8 device and running through our typical regression tests is
> probably the best we can do at this time.
> 
> [Regression Potential]
> 
> Touching the page handling code always carries significant risk.
> However, the fix is simply reverting the change that added the
> execute-only user mappings feature in v4.9.

Applied to focal/master-next and unstable/master, thanks!