macvlan: fix a possible use after free

Commit bc416d9768 (macvlan: handle fragmented multicast frames) added a
possible use after free in macvlan_handle_frame(), since
ip_check_defrag() uses pskb_may_pull() : skb header can be reallocated.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ben Greear <greearb@candelatech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index f2f820c4b40a..9ea99217f116 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -173,6 +173,7 @@ static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb)
                 skb = ip_check_defrag(skb, IP_DEFRAG_MACVLAN);
                 if (!skb)
                         return RX_HANDLER_CONSUMED;
+                eth = eth_hdr(skb);
                 src = macvlan_hash_lookup(port, eth->h_source);
                 if (!src)
                         /* frame comes from an external address */