On 08/09/2013 09:27 AM, Daniel Borkmann wrote:
Probably this one is quite unlikely to be triggered, but it's more safe
to hold a pointer to asoc (instead of dereferencing), free the packet
chunks first, and access asoc though the pointer after we have called
sctp_transport_destroy_rcu() where the transport is being kfree()'d.
Introduced by commit 8c98653f ("sctp: sctp_close: fix release of bindings
for deferred call_rcu's"). I also did the 8c98653f regression test and
it's fine that way.
Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
---
v1->v2: do sctp_packet_free before call_rcu
net/sctp/transport.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index bdbbc3f..c691455 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -176,17 +176,19 @@ static void sctp_transport_destroy_rcu(struct rcu_head *head)
*/
static void sctp_transport_destroy(struct sctp_transport *transport)
{
+ struct sctp_association *asoc = transport->asoc;
+
if (unlikely(!transport->dead)) {
WARN(1, "Attempt to destroy undead transport %p!\n", transport);
return;
}
- call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
-
sctp_packet_free(&transport->packet);
- if (transport->asoc)
- sctp_association_put(transport->asoc);
+ call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
+
+ if (asoc != NULL)
+ sctp_association_put(asoc);
I think it is safe to move call_rcu to be the last call in this
function. This should never be a last ref on the association. If
by some chance it is, we'll get the same warning.
And if you move call_rcu(), this becomes an ever smaller patch :)
-vlad
}
/* Start T3_rtx timer if it is not already running and update the heartbeat
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