From: Ignacio Alvarado Date: Fri, 4 Nov 2016 19:15:55 +0000 (-0700) Subject: KVM: Disable irq while unregistering user notifier X-Git-Tag: v4.14-rc1~2065^2~4 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=1650b4ebc99da4c137bfbfc531be4a2405f951dd;p=platform%2Fkernel%2Flinux-rpi.git KVM: Disable irq while unregistering user notifier Function user_notifier_unregister should be called only once for each registered user notifier. Function kvm_arch_hardware_disable can be executed from an IPI context which could cause a race condition with a VCPU returning to user mode and attempting to unregister the notifier. Signed-off-by: Ignacio Alvarado Cc: stable@vger.kernel.org Fixes: 18863bdd60f8 ("KVM: x86 shared msr infrastructure") Reviewed-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7d3d9d4..2f27af4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -210,7 +210,18 @@ static void kvm_on_user_return(struct user_return_notifier *urn) struct kvm_shared_msrs *locals = container_of(urn, struct kvm_shared_msrs, urn); struct kvm_shared_msr_values *values; + unsigned long flags; + /* + * Disabling irqs at this point since the following code could be + * interrupted and executed through kvm_arch_hardware_disable() + */ + local_irq_save(flags); + if (locals->registered) { + locals->registered = false; + user_return_notifier_unregister(urn); + } + local_irq_restore(flags); for (slot = 0; slot < shared_msrs_global.nr; ++slot) { values = &locals->values[slot]; if (values->host != values->curr) { @@ -218,8 +229,6 @@ static void kvm_on_user_return(struct user_return_notifier *urn) values->curr = values->host; } } - locals->registered = false; - user_return_notifier_unregister(urn); } static void shared_msr_update(unsigned slot, u32 msr)