phonet: properly unshare skbs in phonet_rcv()

Ivaylo Dimitrov reported a regression caused by commit 7866a62 ("dev: add per net_device packet type chains"). skb->dev becomes NULL and we crash in __netif_receive_skb_core(). Before above commit, different kind of bugs or corruptions could happen without major crash. But the root cause is that phonet_rcv() can queue skb without checking if skb is shared or not. Many thanks to Ivaylo Dimitrov for his help, diagnosis and tests. Reported-by: Ivaylo Dimitrov <[email protected]> Tested-by: Ivaylo Dimitrov <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Cc: Remi Denis-Courmont <[email protected]> Signed-off-by: David S. Miller <[email protected]>
chewitt · Jan 12, 2016 · 7aaed57 · 7aaed57
1 parent d461873
commit 7aaed57
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
@@ -377,6 +377,10 @@ static int phonet_rcv(struct sk_buff *skb, struct net_device *dev,
 	struct sockaddr_pn sa;
 	u16 len;
 
+	skb = skb_share_check(skb, GFP_ATOMIC);
+	if (!skb)
+		return NET_RX_DROP;
+
 	/* check we have at least a full Phonet header */
 	if (!pskb_pull(skb, sizeof(struct phonethdr)))
 		goto out;