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

ZhangShurong · takaswie · commit 3ff256751a28 · 2023-06-24T14:03:46.000+09:00
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>
diff --git 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;

Original file line number	Diff line number	Diff line change
`@@ -479,7 +479,7 @@ static int fwnet_finish_incoming_packet(struct net_device *net,`
`479`	`479`	`struct sk_buff *skb, u16 source_node_id,`
`480`	`480`	`bool is_broadcast, u16 ether_type)`
`481`	`481`	`{`
`482`		`- int status;`
	`482`	`+ int status, len;`
`483`	`483`
`484`	`484`	`switch (ether_type) {`
`485`	`485`	`case ETH_P_ARP:`
`@@ -533,13 +533,15 @@ static int fwnet_finish_incoming_packet(struct net_device *net,`
`533`	`533`	`}`
`534`	`534`	`skb->protocol = protocol;`
`535`	`535`	`}`
	`536`	`+`
	`537`	`+ len = skb->len;`
`536`	`538`	`status = netif_rx(skb);`
`537`	`539`	`if (status == NET_RX_DROP) {`
`538`	`540`	`net->stats.rx_errors++;`
`539`	`541`	`net->stats.rx_dropped++;`
`540`	`542`	`} else {`
`541`	`543`	`net->stats.rx_packets++;`
`542`		`- net->stats.rx_bytes += skb->len;`
	`544`	`+ net->stats.rx_bytes += len;`
`543`	`545`	`}`
`544`	`546`
`545`	`547`	`return 0;`