The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From d4a8061a7c5f7c27a2dc002ee4cb89b3e6637e44 Mon Sep 17 00:00:00 2001
From: Heyi Guo <guoheyi@xxxxxxxxxx>
Date: Tue, 27 Aug 2019 12:26:50 +0100
Subject: [PATCH] KVM: arm/arm64: vgic: Fix potential deadlock when ap_list is
long
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@xxxxxxxxxxxxxxx # 4.7+
Fixes: 8e4447457965 ("KVM: arm/arm64: vgic-new: Add IRQ sorting")
Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
Signed-off-by: Heyi Guo <guoheyi@xxxxxxxxxx>
[maz: massaged commit log and patch, added Fixes and Cc-stable]
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 04786c8ec77e..ca5e6c6866a4 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -254,6 +254,13 @@ 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;
+
raw_spin_lock(&irqa->irq_lock);
raw_spin_lock_nested(&irqb->irq_lock, SINGLE_DEPTH_NESTING);
