This is a note to let you know that I've just added the patch titled KVM: arm/arm64: Fix reference to uninitialised VGIC to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-arm-arm64-fix-reference-to-uninitialised-vgic.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From b3aff6ccbb1d25e506b60ccd9c559013903f3464 Mon Sep 17 00:00:00 2001 From: Andre Przywara <andre.przywara@xxxxxxx> Date: Wed, 3 Feb 2016 16:56:51 +0000 Subject: KVM: arm/arm64: Fix reference to uninitialised VGIC From: Andre Przywara <andre.przywara@xxxxxxx> commit b3aff6ccbb1d25e506b60ccd9c559013903f3464 upstream. Commit 4b4b4512da2a ("arm/arm64: KVM: Rework the arch timer to use level-triggered semantics") brought the virtual architected timer closer to the VGIC. There is one occasion were we don't properly check for the VGIC actually having been initialized before, but instead go on to check the active state of some IRQ number. If userland hasn't instantiated a virtual GIC, we end up with a kernel NULL pointer dereference: ========= Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = ffffffc9745c5000 [00000000] *pgd=00000009f631e003, *pud=00000009f631e003, *pmd=0000000000000000 Internal error: Oops: 96000006 [#2] PREEMPT SMP Modules linked in: CPU: 0 PID: 2144 Comm: kvm_simplest-ar Tainted: G D 4.5.0-rc2+ #1300 Hardware name: ARM Juno development board (r1) (DT) task: ffffffc976da8000 ti: ffffffc976e28000 task.ti: ffffffc976e28000 PC is at vgic_bitmap_get_irq_val+0x78/0x90 LR is at kvm_vgic_map_is_active+0xac/0xc8 pc : [<ffffffc0000b7e28>] lr : [<ffffffc0000b972c>] pstate: 20000145 .... ========= Fix this by bailing out early of kvm_timer_flush_hwstate() if we don't have a VGIC at all. Reported-by: Cosmin Gorgovan <cosmin@xxxxxxxxxxxxxx> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- virt/kvm/arm/arch_timer.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -143,7 +143,7 @@ static void kvm_timer_update_irq(struct * Check if there was a change in the timer state (should we raise or lower * the line level to the GIC). */ -static void kvm_timer_update_state(struct kvm_vcpu *vcpu) +static int kvm_timer_update_state(struct kvm_vcpu *vcpu) { struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; @@ -154,10 +154,12 @@ static void kvm_timer_update_state(struc * until we call this function from kvm_timer_flush_hwstate. */ if (!vgic_initialized(vcpu->kvm)) - return; + return -ENODEV; if (kvm_timer_should_fire(vcpu) != timer->irq.level) kvm_timer_update_irq(vcpu, !timer->irq.level); + + return 0; } /* @@ -218,7 +220,8 @@ void kvm_timer_flush_hwstate(struct kvm_ bool phys_active; int ret; - kvm_timer_update_state(vcpu); + if (kvm_timer_update_state(vcpu)) + return; /* * If we enter the guest with the virtual input level to the VGIC Patches currently in stable-queue which might be from andre.przywara@xxxxxxx are queue-4.4/kvm-arm-arm64-fix-reference-to-uninitialised-vgic.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html