[ Upstream commit d4a8061a7c5f7c27a2dc002ee4cb89b3e6637e44 ]
If the ap_list is longer than 256 entries, merge_final() in list_sort() will call the comparison callback with the same element twice, causing a deadlock in vgic_irq_cmp().
Fix it by returning early when irqa == irqb.
Cc: stable@vger.kernel.org # 4.7+ Fixes: 8e4447457965 ("KVM: arm/arm64: vgic-new: Add IRQ sorting") Signed-off-by: Zenghui Yu yuzenghui@huawei.com Signed-off-by: Heyi Guo guoheyi@huawei.com [maz: massaged commit log and patch, added Fixes and Cc-stable] Signed-off-by: Marc Zyngier maz@kernel.org Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- virt/kvm/arm/vgic/vgic.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c index 6440b56ec90e2..1934dc8a2ce09 100644 --- a/virt/kvm/arm/vgic/vgic.c +++ b/virt/kvm/arm/vgic/vgic.c @@ -196,6 +196,13 @@ static int vgic_irq_cmp(void *priv, struct list_head *a, struct list_head *b) bool penda, pendb; int ret;
+ /* + * list_sort may call this function with the same element when + * the list is fairly long. + */ + if (unlikely(irqa == irqb)) + return 0; + spin_lock(&irqa->irq_lock); spin_lock_nested(&irqb->irq_lock, SINGLE_DEPTH_NESTING);