** Description changed:
[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 are
+ 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.
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https://bugs.launchpad.net/bugs/1858815
Title:
PAN is broken for execute-only user mappings on ARMv8
Status in linux package in Ubuntu:
In Progress
Status in linux source package in Bionic:
In Progress
Status in linux source package in Disco:
In Progress
Status in linux source package in Eoan:
In Progress
Status in linux source package in Focal:
In Progress
Bug description:
[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.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1858815/+subscriptions
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