From f35eb8a3aa3b492489116965558c3f2f7d641f31 Mon Sep 17 00:00:00 2001 From: Heyi Guo Date: Tue, 27 Aug 2019 12:26:50 +0100 Subject: KVM: arm/arm64: vgic: Fix potential deadlock when ap_list is long [ 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 Signed-off-by: Heyi Guo [maz: massaged commit log and patch, added Fixes and Cc-stable] Signed-off-by: Marc Zyngier Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- 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 6440b56ec90e..1934dc8a2ce0 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); -- cgit v1.2.3