CVE-2022-48765

In the Linux kernel, the following vulnerability has been resolved:

KVM: LAPIC: Also cancel preemption timer during SET_LAPIC

The below warning is splatting during guest reboot.

————[ cut here ]———— WARNING: CPU: 0 PID: 1931 at arch/x86/kvm/x86.c:10322 kvm_arch_vcpu_ioctl_run+0x874/0x880 [kvm] CPU: 0 PID: 1931 Comm: qemu-system-x86 Tainted: G I 5.17.0-rc1+ #5 RIP: 0010:kvm_arch_vcpu_ioctl_run+0x874/0x880 [kvm] Call Trace: kvm_vcpu_ioctl+0x279/0x710 [kvm] __x64_sys_ioctl+0x83/0xb0 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fd39797350b

This can be triggered by not exposing tsc-deadline mode and doing a reboot in the guest. The lapic_shutdown() function which is called in sys_reboot path will not disarm the flying timer, it just masks LVTT. lapic_shutdown() clears APIC state w/ LVT_MASKED and timer-mode bit is 0, this can trigger timer-mode switch between tsc-deadline and oneshot/periodic, which can result in preemption timer be cancelled in apic_update_lvtt(). However, We cant depend on this when not exposing tsc-deadline mode and oneshot/periodic modes emulated by preemption timer. Qemu will synchronise states around reset, lets cancel preemption timer under KVM_SET_LAPIC.

Affected Software

References

• https://git.kernel.org/stable/c/35fe7cfbab2e81f1afb23fc4212210b1de6d9633
• https://git.kernel.org/stable/c/54b3439c8e70e0bcfea59aeef9dd98908cbbf655
• https://git.kernel.org/stable/c/ce55f63f6cea4cab8ae9212f73285648a5baa30d