net: systemport: Guard against unmapped TX ring

ffainelli · davem330 · commit e83b171568e6 · 2017-10-23T05:28:40.000+01:00
Because SYSTEMPORT is a (semi) normal network device, the stack may attempt to
queue packets on it oustide of the DSA slave transmit path.  When that happens,
the DSA layer has not had a chance to tag packets with the appropriate per-port
and per-queue information, and if that happens and we don't have a port 0 queue
0 available (e.g: on boards where this does not exist), we will hit a NULL
pointer de-reference in bcm_sysport_select_queue().

Guard against such cases by testing for the TX ring validity.

Fixes: 84ff33eeb23d ("net: systemport: Establish DSA network device queue mapping")
Signed-off-by: Florian Fainelli &lt;f.fainelli@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c b/drivers/net/ethernet/broadcom/bcmsysport.c
@@ -2040,6 +2040,9 @@ static u16 bcm_sysport_select_queue(struct net_device *dev, struct sk_buff *skb,
 	port = BRCM_TAG_GET_PORT(queue);
 	tx_ring = priv->ring_map[q + port * priv->per_port_num_tx_queues];
 
+	if (unlikely(!tx_ring))
+		return fallback(dev, skb);
+
 	return tx_ring->index;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -2040,6 +2040,9 @@ static u16 bcm_sysport_select_queue(struct net_device dev, struct sk_buff skb,`
`2040`	`2040`	`port = BRCM_TAG_GET_PORT(queue);`
`2041`	`2041`	`tx_ring = priv->ring_map[q + port * priv->per_port_num_tx_queues];`
`2042`	`2042`
	`2043`	`+ if (unlikely(!tx_ring))`
	`2044`	`+ return fallback(dev, skb);`
	`2045`	`+`
`2043`	`2046`	`return tx_ring->index;`
`2044`	`2047`	`}`
`2045`	`2048`