inet_diag: fix access to tcp cc information

Two different problems are fixed here :

1) inet_sk_diag_fill() might be called without socket lock held.
   icsk->icsk_ca_ops can change under us and module be unloaded.
   -> Access to freed memory.
   Fix this using rcu_read_lock() to prevent module unload.

2) Some TCP Congestion Control modules provide information
   but again this is not safe against icsk->icsk_ca_ops
   change and nla_put() errors were ignored. Some sockets
   could not get the additional info if skb was almost full.

Fix this by returning a status from get_info() handlers and
using rcu protection as well.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index bb63fba47d47..b3c57cceb990 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -256,8 +256,7 @@ static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
 }
 
 /* Extract info for Tcp socket info provided via netlink. */
-static void tcp_westwood_info(struct sock *sk, u32 ext,
-			      struct sk_buff *skb)
+static int tcp_westwood_info(struct sock *sk, u32 ext, struct sk_buff *skb)
 {
 	const struct westwood *ca = inet_csk_ca(sk);
 
@@ -268,8 +267,9 @@ static void tcp_westwood_info(struct sock *sk, u32 ext,
 			.tcpv_minrtt = jiffies_to_usecs(ca->rtt_min),
 		};
 
-		nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info);
+		return nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info);
 	}
+	return 0;
 }
 
 static struct tcp_congestion_ops tcp_westwood __read_mostly = {