On Thu, Dec 15, 2016 at 11:00:55PM +0800, Xin Long wrote:
> Since commit 7fda702f9315 ("sctp: use new rhlist interface on sctp transport
> rhashtable"), sctp has changed to use rhlist_lookup to look up transport, but
> rhlist_lookup doesn't call rcu_read_lock inside, unlike rhashtable_lookup_fast.
>
> It is called in sctp_epaddr_lookup_transport and sctp_addrs_lookup_transport.
> sctp_addrs_lookup_transport is always in the protection of rcu_read_lock(),
> as __sctp_lookup_association is called in rx path or sctp_lookup_association
> which are in the protection of rcu_read_lock() already.
>
> But sctp_epaddr_lookup_transport is called by sctp_endpoint_lookup_assoc, it
> doesn't call rcu_read_lock, which may cause "suspicious rcu_dereference_check
> usage' in __rhashtable_lookup.
>
> This patch is to fix it by adding rcu_read_lock in sctp_endpoint_lookup_assoc
> before calling sctp_epaddr_lookup_transport.
>
> Fixes: 7fda702f9315 ("sctp: use new rhlist interface on sctp transport rhashtable")
> Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> ---
> net/sctp/endpointola.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/sctp/endpointola.c b/net/sctp/endpointola.c
> index 1f03065..410ddc1 100644
> --- a/net/sctp/endpointola.c
> +++ b/net/sctp/endpointola.c
> @@ -331,7 +331,9 @@ struct sctp_association *sctp_endpoint_lookup_assoc(
> * on this endpoint.
> */
> if (!ep->base.bind_addr.port)
> - goto out;
> + return NULL;
> +
> + rcu_read_lock();
> t = sctp_epaddr_lookup_transport(ep, paddr);
> if (!t)
> goto out;
> @@ -339,6 +341,7 @@ struct sctp_association *sctp_endpoint_lookup_assoc(
> *transport = t;
> asoc = t->asoc;
> out:
> + rcu_read_unlock();
> return asoc;
> }
>
> --
> 2.1.0
>
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