Type confusion

The fixes for XSA-422 Branch Type Confusion and XSA-434 Speculative Return Stack Overflow are not IRQ-safe. It was believed that the mitigations always operated in contexts with IRQs disabled. However, the original XSA-254 fix for Meltdown XPTI deliberately left interrupts enabled on two entry...

x86: PV guest may crash Xen with XPTI

ISSUE DESCRIPTION The workaround for the Meltdown vulnerability XSA-254 failed to deal with an error code path connecting the INT 80 handling with general exception handling. This results in an unconditional write attempt of the value zero to an address near 2^64, in cases where a PV guest has no...