[PATCH] net: Fix oops from tcp_collapse() when using splice()

["Steven J. Magnani" <steve@digidescorp.com>]

tcp_read_sock() can have a eat skbs without immediately advancing copied_seq.
This can cause a panic in tcp_collapse() if it is called as a result
of the recv_actor dropping the socket lock.

A userspace program that splices data from a socket to either another
socket or to a file can trigger this bug.

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
---
diff -uprN a/net/ipv4/tcp.c b/net/ipv4/tcp.c
--- a/net/ipv4/tcp.c	2010-03-30 15:25:55.000000000 -0500
+++ b/net/ipv4/tcp.c	2010-03-30 15:27:49.000000000 -0500
@@ -1335,6 +1335,7 @@ int tcp_read_sock(struct sock *sk, read_
 		sk_eat_skb(sk, skb, 0);
 		if (!desc->count)
 			break;
+		tp->copied_seq = seq;
 	}
 	tp->copied_seq = seq;