KVM: x86: Cancel pvclock_gtod_work on module removal

Nothing prevents the following:

  pvclock_gtod_notify()
    queue_work(system_long_wq, &pvclock_gtod_work);
  ...
  remove_module(kvm);
  ...
  work_queue_run()
    pvclock_gtod_work()	<- UAF

Ditto for any other operation on that workqueue list head which touches
pvclock_gtod_work after module removal.

Cancel the work in kvm_arch_exit() to prevent that.

Fixes: 16e8d74d2da9 ("KVM: x86: notifier for clocksource changes")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Message-Id: <87czu4onry.ffs@nanos.tec.linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9b1a704..259139a 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8224,6 +8224,7 @@ void kvm_arch_exit(void)
        cpuhp_remove_state_nocalls(CPUHP_AP_X86_KVM_CLK_ONLINE);
 #ifdef CONFIG_X86_64
        pvclock_gtod_unregister_notifier(&pvclock_gtod_notifier);
+       cancel_work_sync(&pvclock_gtod_work);
 #endif
        kvm_x86_ops.hardware_enable = NULL;
        kvm_mmu_module_exit();