vxlan: vnifilter: fix spurious notification on VNI update

[ Upstream commit 84683b5b60 ]

When a VNI is re-added with the same attributes (e.g. same group or no
group), vxlan_vni_update() sends a spurious RTM_NEWTUNNEL notification
even though nothing changed.

The bug is that 'if (changed)' tests whether the pointer is non-NULL,
not the bool value it points to. Since every caller passes a valid
pointer, the condition is always true and the notification fires
unconditionally.

Fix by dereferencing the pointer: 'if (*changed)'.

Reproducer:

 # ip link add vxlan100 type vxlan dstport 4789 local 10.0.0.1 \
      nolearning external vnifilter
 # ip link set vxlan100 up
 # bridge monitor vni &
 # bridge vni add vni 1000 dev vxlan100
 # bridge vni add vni 1000 dev vxlan100  # spurious notification

Fixes: f9c4bb0b24 ("vxlan: vni filtering support on collect metadata device")
Signed-off-by: Andy Roulin <aroulin@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20260602185138.253265-3-aroulin@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/vxlan/vxlan_vnifilter.c

@@ -671,7 +671,7 @@ static int vxlan_vni_update(struct vxlan_dev *vxlan,
 	if (ret)
 		return ret;
 
-	if (changed)
+	if (*changed)
 		vxlan_vnifilter_notify(vxlan, vninode, RTM_NEWTUNNEL);
 
 	return 0;