qeth: l3 fix rcu splat in xmit

when use dst_get_neighbour to get neighbour, we need
rcu_read_lock to protect, since dst_get_neighbour uses
rcu_dereference.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index e4c1176ee25b..4d5307ddbe55 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2756,11 +2756,13 @@ int inline qeth_l3_get_cast_type(struct qeth_card *card, struct sk_buff *skb)
         struct neighbour *n = NULL;
         struct dst_entry *dst;
 
+        rcu_read_lock();
         dst = skb_dst(skb);
         if (dst)
                 n = dst_get_neighbour(dst);
         if (n) {
                 cast_type = n->type;
+                rcu_read_unlock();
                 if ((cast_type == RTN_BROADCAST) ||
                     (cast_type == RTN_MULTICAST) ||
                     (cast_type == RTN_ANYCAST))
@@ -2768,6 +2770,8 @@ int inline qeth_l3_get_cast_type(struct qeth_card *card, struct sk_buff *skb)
                 else
                         return RTN_UNSPEC;
         }
+        rcu_read_unlock();
+
         /* try something else */
         if (skb->protocol == ETH_P_IPV6)
                 return (skb_network_header(skb)[24] == 0xff) ?
@@ -2847,6 +2851,8 @@ static void qeth_l3_fill_header(struct qeth_card *card, struct qeth_hdr *hdr,
         }
 
         hdr->hdr.l3.length = skb->len - sizeof(struct qeth_hdr);
+
+        rcu_read_lock();
         dst = skb_dst(skb);
         if (dst)
                 n = dst_get_neighbour(dst);
@@ -2893,6 +2899,7 @@ static void qeth_l3_fill_header(struct qeth_card *card, struct qeth_hdr *hdr,
                                 QETH_CAST_UNICAST | QETH_HDR_PASSTHRU;
                 }
         }
+        rcu_read_unlock();
 }
 
 static inline void qeth_l3_hdr_csum(struct qeth_card *card,