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>

3 files changed, 10 insertions, 2 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4667d4d7c162..f2913ae2b52c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2992,7 +2992,11 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
         memset(serr, 0, sizeof(*serr));
         serr->ee.ee_errno = ENOMSG;
         serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
+
+        bh_lock_sock(sk);
         err = sock_queue_err_skb(sk, skb);
+        bh_unlock_sock(sk);
+
         if (err)
                 kfree_skb(skb);
 }
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index b9d0d409516f..acdc9be833cc 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -634,7 +634,9 @@ void __udp4_lib_err(struct sk_buff *skb, u32 info, struct udp_table *udptable)
                 if (!harderr || sk->sk_state != TCP_ESTABLISHED)
                         goto out;
         } else {
+                bh_lock_sock(sk);
                 ip_icmp_error(sk, skb, err, uh->dest, info, (u8 *)(uh+1));
+                bh_unlock_sock(sk);
         }
         sk->sk_err = err;
         sk->sk_error_report(sk);
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: