KVM: x86/xen: Initialize Xen timer only once

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86/xen: Initialize Xen timer only once Add a check for existing xen timers before initializing a new one. Currently kvm_xen_init_timer() is called on every KVM_XEN_VCPU_ATTR_TYPE_TIMER, which is causing the following ODEBUG crash when vcpu->arch.xen.timer is already set. ODEBUG: init active (active state 0) object type: hrtimer hint: xen_timer_callbac0 RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:502 Call Trace: __debug_object_init debug_hrtimer_init debug_init hrtimer_init kvm_xen_init_timer kvm_xen_vcpu_set_attr kvm_arch_vcpu_ioctl kvm_vcpu_ioctl vfs_ioctl

References

• https://git.kernel.org/stable/c/9a9b5771e930f408c3419799000f76a9abaf2278
• https://git.kernel.org/stable/c/af735db31285fa699384c649be72a9f32ecbb665