macvlan: fix a possible use after free

[ Upstream commit 4ec7ac1203bcf21f5e3d977c9818b1a56c9ef40d ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 7413497..959d448 100644 (file)
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -172,6 +172,7 @@ 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 */