ipv4: Fix route refcount on pmtu discovery

PATCH Applied Steffen Klassert 2 participants 2 messages Jan 22, 2013

Subsystems (3)

Networking Network drivers IPv4/IPv6

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Steffen Klassert

author

2013-01-22 10:01 UTC #0 lore raw

PATCH 1/1 ipv4: Fix route refcount on pmtu discovery

git commit 9cb3a50c (ipv4: Invalidate the socket cached route on pmtu events if possible) introduced a refcount problem. We don't get a refcount on the route if we get it from__sk_dst_get(), but we need one if we want to reuse this route because __sk_dst_set() releases the refcount of the old route. This patch adds proper refcount handling for that case. We introduce a 'new' flag to indicate that we are going to use a new route and we release the old route only if we replace it by a new one.

Reported-by Julian Anastasov <[email protected]>

Signed-off-by Steffen Klassert <[email protected]>

---
 net/ipv4/route.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

net/ipv4/route.c +9 -2

index 132737a..a0fcc47 100644
@@ -985,6 +985,7 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu)
 	struct flowi4 fl4;
 	struct rtable *rt;
 	struct dst_entry *dst;
+	bool new = false;
 
 	bh_lock_sock(sk);
 	rt = (struct rtable *) __sk_dst_get(sk);

@@ -1000,20 +1001,26 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu)
 		rt = ip_route_output_flow(sock_net(sk), &fl4, sk);
 		if (IS_ERR(rt))
 			goto out;
+
+		new = true;
 	}
 
 	__ip_rt_update_pmtu((struct rtable *) rt->dst.path, &fl4, mtu);
 
 	dst = dst_check(&rt->dst, 0);
 	if (!dst) {
+		if (new)
+			dst_release(&rt->dst);
+
 		rt = ip_route_output_flow(sock_net(sk), &fl4, sk);
 		if (IS_ERR(rt))
 			goto out;
 
-		dst = &rt->dst;
+		new = true;
 	}
 
-	 __sk_dst_set(sk, dst);
+	if (new)
+		__sk_dst_set(sk, &rt->dst);
 
 out:
 	bh_unlock_sock(sk);

Signature · 1 line

1.7.9.5

David Miller

maintainer Applied

2013-01-22 19:23 UTC #1 lore raw

From: Steffen Klassert <[email protected]>
Date: Tue, 22 Jan 2013 11:01:28 +0100

Quoted 11 lines

git commit 9cb3a50c (ipv4: Invalidate the socket cached route on pmtu events if possible) introduced a refcount problem. We don't get a refcount on the route if we get it from__sk_dst_get(), but we need one if we want to reuse this route because __sk_dst_set() releases the refcount of the old route. This patch adds proper refcount handling for that case. We introduce a 'new' flag to indicate that we are going to use a new route and we release the old route only if we replace it by a new one.
Reported-by Julian Anastasov <[email protected]>
Signed-off-by Steffen Klassert <[email protected]>

Applied, thanks.