Hi, On 03/08/16 17:13, Christoffer Dall wrote: > Right now the following sequence of events can happen: > > 1. Thread X calls vgic_put_irq > 2. Thread Y calls vgic_add_lpi > 3. Thread Y gets lpi_list_lock > 4. Thread X drops the ref count to 0 and blocks on lpi_list_lock > 5. Thread Y finds the irq via the lpi_list_lock, raises the ref > count to 1, and release the lpi_list_lock. > 6. Thread X proceeds and frees the irq. > > Avoid this by holding the spinlock around the kref_put. > > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > --- > virt/kvm/arm/vgic/vgic.c | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c > index e7aeac7..fb8c0ab 100644 > --- a/virt/kvm/arm/vgic/vgic.c > +++ b/virt/kvm/arm/vgic/vgic.c > @@ -117,22 +117,22 @@ static void vgic_irq_release(struct kref *ref) > > void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq) > { > - struct vgic_dist *dist; > + struct vgic_dist *dist = &kvm->arch.vgic; > > if (irq->intid < VGIC_MIN_LPI) > return; > > - if (!kref_put(&irq->refcount, vgic_irq_release)) > - return; > - > - dist = &kvm->arch.vgic; > - > spin_lock(&dist->lpi_list_lock); > - list_del(&irq->lpi_list); > - dist->lpi_list_count--; > - spin_unlock(&dist->lpi_list_lock); > + if (!kref_put(&irq->refcount, vgic_irq_release)) { > + spin_unlock(&dist->lpi_list_lock); > + return; > + } else { Just a nit, I guess, but we don't need this "else" since the if-branch always returns? > + list_del(&irq->lpi_list); > + dist->lpi_list_count--; > + spin_unlock(&dist->lpi_list_lock); > > - kfree(irq); > + kfree(irq); > + } > } > > /** > Otherwise: Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx> Cheers, Andre. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html