KVM: x86: Ignore pending PV EOI if the vCPU has since disabled PV EOIs

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Ignore pending PV EOI if the vCPU has since disabled PV EOIs Ignore KVM's internal "service pending PV EOI" request if the vCPU has disabled PV EOIs since the request was made. Asserting that PV EOIs are enabled can fail if reading guest memory in pv_eoi_get_user() fails, i.e. if pv_eoi_test_and_clr_pending() bails early, *and* the vCPU also disables PV EOIs. kernel BUG at arch/x86/kvm/lapic.c:3338! Oops: invalid opcode: 0000 [#1] SMP CPU: 4 UID: 1000 PID: 890 Comm: pv_eoi_test Not tainted 7.0.0-d585aa5894d8-vm #337 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:kvm_lapic_sync_from_vapic+0x12b/0x140 [kvm] Call Trace: <TASK> kvm_arch_vcpu_ioctl_run+0x1075/0x1c30 [kvm] kvm_vcpu_ioctl+0x2d5/0x980 [kvm] __x64_sys_ioctl+0x8a/0xd0 do_syscall_64+0xb5/0xb40 entry_SYSCALL_64_after_hwframe+0x4b/0x53 </TASK> Modules linked in: kvm_intel kvm irqbypass ---[ end trace 0000000000000000 ]---