[PATCH 4.9 214/240] KVM: x86: Cancel pvclock_gtod_work on module removal

Greg Kroah-Hartman
2021-05-20T11:24:24Z

From: Thomas Gleixner <tglx@linutronix.de>

commit 594b27e677b35f9734b1969d175ebc6146741109 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/x86.c | 1 +
1 file changed, 1 insertion(+)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6268,6 +6268,7 @@ 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 = NULL;
kvm_mmu_module_exit();