From: Vlad Yasevich <vyasevich@gmail•com>
To: Daniel Borkmann <dborkman@redhat•com>
Cc: davem@davemloft•net, netdev@vger•kernel.org, linux-sctp@vger•kernel.org
Subject: Re: [PATCH net v2] net: sctp: sctp_transport_destroy{,_rcu}: fix potential pointer corruption
Date: Fri, 09 Aug 2013 09:57:47 -0400 [thread overview]
Message-ID: <5204F55B.2040704@gmail.com> (raw)
In-Reply-To: <1376054842-376-1-git-send-email-dborkman@redhat.com>
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@redhat•com>
> ---
> 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
>
next prev parent reply other threads:[~2013-08-09 13:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-09 13:27 [PATCH net v2] net: sctp: sctp_transport_destroy{,_rcu}: fix potential pointer corruption Daniel Borkmann
2013-08-09 13:57 ` Vlad Yasevich [this message]
2013-08-09 13:59 ` Daniel Borkmann
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