firewire: net: fix use after free in fwnet_finish_incoming_packet()

[ Upstream commit 3ff256751a2853e1ffaa36958ff933ccc98c6cb5 ]

The netif_rx() function frees the skb so we can't dereference it to
save the skb->len.

Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
Link: https://lore.kernel.org/r/tencent_3B3D24B66ED66A6BB73CC0E63C6A14E45109@qq.com
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
index af22be8..a53eace 100644 (file)
--- a/drivers/firewire/net.c
+++ b/drivers/firewire/net.c
@@ -479,7 +479,7 @@ static int fwnet_finish_incoming_packet(struct net_device *net,
                                        struct sk_buff *skb, u16 source_node_id,
                                        bool is_broadcast, u16 ether_type)
 {
-       int status;
+       int status, len;
 
        switch (ether_type) {
        case ETH_P_ARP:
@@ -533,13 +533,15 @@ static int fwnet_finish_incoming_packet(struct net_device *net,
                }
                skb->protocol = protocol;
        }
+
+       len = skb->len;
        status = netif_rx(skb);
        if (status == NET_RX_DROP) {
                net->stats.rx_errors++;
                net->stats.rx_dropped++;
        } else {
                net->stats.rx_packets++;
-               net->stats.rx_bytes += skb->len;
+               net->stats.rx_bytes += len;
        }
 
        return 0;