net: fix sk_forward_alloc corruptions

As David found out, sock_queue_err_skb() should be called with socket
lock hold, or we risk sk_forward_alloc corruption, since we use non
atomic operations to update this field.

This patch adds bh_lock_sock()/bh_unlock_sock() pair to three spots.
(BH already disabled)

1) skb_tstamp_tx() 
2) Before calling ip_icmp_error(), in __udp4_lib_err() 
3) Before calling ipv6_icmp_error(), in __udp6_lib_err()

Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 87be58673b55..3048f906c042 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -466,9 +466,11 @@ void __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
         if (sk->sk_state != TCP_ESTABLISHED && !np->recverr)
                 goto out;
 
-        if (np->recverr)
+        if (np->recverr) {
+                bh_lock_sock(sk);
                 ipv6_icmp_error(sk, skb, err, uh->dest, ntohl(info), (u8 *)(uh+1));
-
+                bh_unlock_sock(sk);
+        }
         sk->sk_err = err;
         sk->sk_error_report(sk);
 out: