From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 5 May 2021 21:48:17 +0000 (+0200)
Subject: KVM: x86: Cancel pvclock_gtod_work on module removal
X-Git-Tag: v4.4.269~18
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5822103eb6af0acc30b06f545078666781044172;p=thirdparty%2Fkernel%2Fstable.git

KVM: x86: Cancel pvclock_gtod_work on module removal

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>
---

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ef920da075184..4b8c83100fad5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6016,6 +6016,7 @@ void kvm_arch_exit(void)
 	unregister_hotcpu_notifier(&kvmclock_cpu_notifier_block);
 #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();