On Mon, Feb 05, 2018 at 09:48:14PM +0200, Tommi Rantala wrote:
> Fix dst reference count leak in sctp_v4_get_dst() introduced in commit
> 410f03831 ("sctp: add routing output fallback"):
>
> When walking the address_list, successive ip_route_output_key() calls
> may return the same rt->dst with the reference incremented on each call.
>
> The code would not decrement the dst refcount when the dst pointer was
> identical from the previous iteration, causing the dst refcnt leak.
>
> Testcase:
> ip netns add TEST
> ip netns exec TEST ip link set lo up
> ip link add dummy0 type dummy
> ip link add dummy1 type dummy
> ip link add dummy2 type dummy
> ip link set dev dummy0 netns TEST
> ip link set dev dummy1 netns TEST
> ip link set dev dummy2 netns TEST
> ip netns exec TEST ip addr add 192.168.1.1/24 dev dummy0
> ip netns exec TEST ip link set dummy0 up
> ip netns exec TEST ip addr add 192.168.1.2/24 dev dummy1
> ip netns exec TEST ip link set dummy1 up
> ip netns exec TEST ip addr add 192.168.1.3/24 dev dummy2
> ip netns exec TEST ip link set dummy2 up
> ip netns exec TEST sctp_test -H 192.168.1.2 -P 20002 -h 192.168.1.1 -p 20000 -s -B 192.168.1.3
> ip netns del TEST
>
> In 4.4 and 4.9 kernels this results to:
> [ 354.179591] unregister_netdevice: waiting for lo to become free. Usage count = 1
> [ 364.419674] unregister_netdevice: waiting for lo to become free. Usage count = 1
> [ 374.663664] unregister_netdevice: waiting for lo to become free. Usage count = 1
> [ 384.903717] unregister_netdevice: waiting for lo to become free. Usage count = 1
> [ 395.143724] unregister_netdevice: waiting for lo to become free. Usage count = 1
> [ 405.383645] unregister_netdevice: waiting for lo to become free. Usage count = 1
> ...
>
> Fixes: 410f03831 ("sctp: add routing output fallback")
> Fixes: 0ca50d12f ("sctp: fix src address selection if using secondary addresses")
> Signed-off-by: Tommi Rantala <tommi.t.rantala@xxxxxxxxx>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Thanks
> ---
>
> v2: unconditional dst_release() before breaking out of the loop:
> - if dst == NULL, then dst_release() is no-op.
> - if dst != &rt->dst, then drop reference to the first dst, we do not
> need it after all.
> - if dst == &rt->dst, then the refcnt was incremented twice for this
> dst, so drop the second ref.
>
> net/sctp/protocol.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index ba28d270eb24..aba2381d3cf9 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -509,22 +509,20 @@ static void sctp_v4_get_dst(struct sctp_transport *t, union sctp_addr *saddr,
> if (IS_ERR(rt))
> continue;
>
> - if (!dst)
> - dst = &rt->dst;
> -
> /* Ensure the src address belongs to the output
> * interface.
> */
> odev = __ip_dev_find(sock_net(sk), laddr->a.v4.sin_addr.s_addr,
> false);
> if (!odev || odev->ifindex != fl4->flowi4_oif) {
> - if (&rt->dst != dst)
> + if (!dst)
> + dst = &rt->dst;
> + else
> dst_release(&rt->dst);
> continue;
> }
>
> - if (dst != &rt->dst)
> - dst_release(dst);
> + dst_release(dst);
> dst = &rt->dst;
> break;
> }
> --
> 2.15.1
>
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