Re: Panic with demuxed ipv4 multicast udp sockets on 4.0.4
From: Eric Dumazet <hidden>
Date: 2015-07-31 10:17:50
Subsystem:
networking [general], the rest, user datagram protocol (udp) · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Willem de Bruijn
On Thu, 2015-07-30 at 22:29 +0000, Gregory Hoggarth wrote:
Hi Eric, Thanks for the patch. I have put this into our code and we'll run our test over tonight and the weekend and report back on Monday. Thanks,
Oh well, real fix will be : (Or at least test if DST_NOCACHE is set : those dst need special care)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 83aa604f9273..470196cb50b8 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c@@ -1995,12 +1995,12 @@ void udp_v4_early_demux(struct sk_buff *skb) skb->sk = sk; skb->destructor = sock_efree; - dst = sk->sk_rx_dst; + dst = READ_ONCE(sk->sk_rx_dst); if (dst) dst = dst_check(dst, 0); - if (dst) - skb_dst_set_noref(skb, dst); + if (dst && atomic_inc_not_zero(&dst->__refcnt)) + skb_dst_set(skb, dst); } int udp_rcv(struct sk_buff *skb)