KVM: x86: Reset IRTE to host control if *new* route isn't postable

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Reset IRTE to host control if *new* route isn't postable Restore an IRTE back to host control (remapped or posted MSI mode) if the *new* GSI route prevents posting the IRQ directly to a vCPU, regardless of the GSI routing type. Updating the IRTE if and only if the new GSI is an MSI results in KVM leaving an IRTE posting to a vCPU. The dangling IRTE can result in interrupts being incorrectly delivered to the guest, and in the worst case scenario can result in use-after-free, e.g. if the VM is torn down, but the underlying host IRQ isn't freed.

References

• https://git.kernel.org/stable/c/e5f2dee9f7fcd2ff4b97869f3c66a0d89c167769
• https://git.kernel.org/stable/c/116c7d35b8f72eac383b9fd371d7c1a8ffc2968b
• https://git.kernel.org/stable/c/023816bd5fa46fab94d1e7917fe131b79ed1fb41
• https://git.kernel.org/stable/c/3481fd96d801715942b6f69fe251133128156f30
• https://git.kernel.org/stable/c/b5de7ac74f69603ad803c524b840bffd36368fc3
• https://git.kernel.org/stable/c/3066ec21d1a33896125747f68638725f456308db
• https://git.kernel.org/stable/c/9bcac97dc42d2f4da8229d18feb0fe2b1ce523a2