On 05.02.2018 03:01, Marcelo Ricardo Leitner wrote:
Hi,
On Sun, Feb 04, 2018 at 11:02:39AM +0200, Tommi Rantala wrote:
Fix dst reference 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 leak.
Ugh, I think this patch still does not get the refcounting right, please
don't apply.
For example:
- on first iteration of the loop:
"odev" check fails, and we set dst with refcnt=1.
- on second iteration:
the same dst refcnt is incremented to 2 via ip_route_output_key().
"odev" check succeeds.
dst == &rt->dst, so we do not touch the refcnt.
break out of the loop
=> oops, dst has refcnt=2
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
Thanks for the detailed steps. I'll adapt and include it on
github/sctp/sctp-tests
ok, good!
In 4.4 and 4.9 kernels this results to:
I wonder why you couldn't reproduce this on newer kernels. Maybe
something masked it?
I didn't check what exactly changed here.
commit 955ec4cb3b54c7c389a9f830be7d3ae2056b9212 was mentioned elsewhere.
Also the commits by Wei Wang changed the dst handling, see e.g.
5b7c9a8ff828287af5aebe93e707271bf1a82cc3
[ 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")
Acked-by: Neil Horman <nhor...@tuxdriver.com>
Cc: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>
Cc: Alexey Kodanev <alexey.koda...@oracle.com>
Signed-off-by: Tommi Rantala <tommi.t.rant...@nokia.com>
---
net/sctp/protocol.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 8b4ff315695e..aadb9e7f60e2 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -508,21 +508,20 @@ 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)
+ if (dst && dst != &rt->dst)
dst_release(dst);
dst = &rt->dst;
break;
--
2.15.1
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