[ 48/61] ipv4: Fix route refcount on pmtu discovery

From: Greg Kroah-Hartman
Date: Tue Feb 12 2013 - 15:36:20 EST

3.7-stable review patch. If anyone has any objections, please let me know.


From: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>

[ Upstream commit b44108dbdbaa07c609bb5755e8dd6c2035236251 ]

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 <ja@xxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/ipv4/route.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -985,6 +985,7 @@ void ipv4_sk_update_pmtu(struct sk_buff
struct flowi4 fl4;
struct rtable *rt;
struct dst_entry *dst;
+ bool new = false;

rt = (struct rtable *) __sk_dst_get(sk);
@@ -1000,20 +1001,26 @@ void ipv4_sk_update_pmtu(struct sk_buff
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);


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/