Comment 0 for bug 1858815

Revision history for this message
Tyler Hicks (tyhicks) wrote :

[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 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.