[PATCH 5.15 285/374] KVM: arm64: vgic-its: Avoid potential UAF in LPI translation cache

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5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver Upton <oliver.upton@xxxxxxxxx>

commit ad362fe07fecf0aba839ff2cc59a3617bd42c33f upstream.

There is a potential UAF scenario in the case of an LPI translation
cache hit racing with an operation that invalidates the cache, such
as a DISCARD ITS command. The root of the problem is that
vgic_its_check_cache() does not elevate the refcount on the vgic_irq
before dropping the lock that serializes refcount changes.

Have vgic_its_check_cache() raise the refcount on the returned vgic_irq
and add the corresponding decrement after queueing the interrupt.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240104183233.3560639-1-oliver.upton@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/arm64/kvm/vgic/vgic-its.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -584,7 +584,11 @@ static struct vgic_irq *vgic_its_check_c
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
+
 	irq = __vgic_its_check_cache(dist, db, devid, eventid);
+	if (irq)
+		vgic_get_irq_kref(irq);
+
 	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
 
 	return irq;
@@ -763,6 +767,7 @@ int vgic_its_inject_cached_translation(s
 	raw_spin_lock_irqsave(&irq->irq_lock, flags);
 	irq->pending_latch = true;
 	vgic_queue_irq_unlock(kvm, irq, flags);
+	vgic_put_irq(kvm, irq);
 
 	return 0;
 }






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