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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@vger.kernel.org # 4.7+
Fixes: 8e44474579 ("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>
This commit is contained in:
Heyi Guo 2019-08-27 12:26:50 +01:00 committed by Will Deacon
parent 2a1a3fa0f2
commit d4a8061a7c
1 changed files with 7 additions and 0 deletions
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7
virt/kvm/arm/vgic/vgic.c
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@ -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);