On 28 November 2016 at 17:00, Ben Pfaff <[email protected]> wrote:
> On Fri, Oct 21, 2016 at 11:47:54AM -0700, Pravin Shelar wrote:
>> On Fri, Oct 21, 2016 at 11:39 AM, Joe Stringer <[email protected]> wrote:
>> > On 21 October 2016 at 11:37, Joe Stringer <[email protected]> wrote:
>> >> On 21 October 2016 at 10:55, Pravin B Shelar <[email protected]> wrote:
>> >>> On upstream kernel datapath OVS make use of networking devices
>> >>> where networking stack does check if device is UP. following
>> >>> patch adds same check in case of compat tunneling implementation.
>> >>> This check also fixes kernel crash in case vxlan device was
>> >>> brought down by user.
>> >>>
>> >>> CPU: 4 PID: 12988 Comm: handler903 Tainted:
>> >>> RIP: 0010:[<ffffffffa05e5407>] vxlan_xmit_one.constprop.50+0x47/0x1210
>> >>> [openvswitch]
>> >>> Call Trace:
>> >>> [<ffffffffa05e6625>] rpl_vxlan_xmit+0x55/0x80 [openvswitch]
>> >>> [<ffffffffa05d5ad4>] ovs_vport_send+0x44/0xb0 [openvswitch]
>> >>> [<ffffffffa05c62a5>] do_output+0x65/0x180 [openvswitch]
>> >>> [<ffffffffa05c70dc>] do_execute_actions+0x10c/0x860 [openvswitch]
>> >>> [<ffffffffa05c7870>] ovs_execute_actions+0x40/0x130 [openvswitch]
>> >>> [<ffffffffa05cbb59>] ovs_packet_cmd_execute+0x2c9/0x2f0 [openvswitch]
>> >>> [<ffffffff8155f31d>] genl_family_rcv_msg+0x1cd/0x400
>> >>> [<ffffffff8155f5e1>] genl_rcv_msg+0x91/0xd0
>> >>> [<ffffffff8155d549>] netlink_rcv_skb+0xa9/0xc0
>> >>> [<ffffffff8155da78>] genl_rcv+0x28/0x40
>> >>> [<ffffffff8155ceba>] netlink_unicast+0x16a/0x210
>> >>> [<ffffffff8155d277>] netlink_sendmsg+0x317/0x430
>> >>> [<ffffffff81514fd0>] sock_sendmsg+0xb0/0xf0
>> >>> [<ffffffff81515409>] ___sys_sendmsg+0x3a9/0x3c0
>> >>> [<ffffffff815162f1>] __sys_sendmsg+0x51/0x90
>> >>> [<ffffffff81516342>] SyS_sendmsg+0x12/0x20
>> >>> [<ffffffff81649609>] system_call_fastpath+0x16/0x1b
>> >>>
>> >>> Reported-by: Huanglili (lee) <[email protected]>
>> >>> Signed-off-by: Pravin B Shelar <[email protected]>
>> >>
>> >> I'm not 100% convinced that this solves the issue (or whether this
>> >> affects upstream as well), but it seems like this at least makes it
>> >> significantly less likely to crash - If I understand correctly,
>> >> setting the vxlan port down currently guarantees a crash, whereas this
>> >> patch would mean it either doesn't crash, or it only crashes based on
>> >> a race condition. Specifically, one where the reconfiguration gets
>> >> past the synchronize_net() into ndo_stop() (before clearing IFF_UP)
>> >> while OVS manages to execute all of a flow up until output and
>> >> proceeds past this check before the reconfiguration thread clears it.
>> >>
>> >> Probably the type of test to check this would be running heavy traffic
>> >> through a vxlan port, then toggle the port up and down.
>> >>
>> >> Will you also check upstream?
>> >>
>> >> Anyway, this LGTM so:
>> >> Acked-by: Joe Stringer <[email protected]>
>> >
>> > Hmm, the original reporter said that the issue is not fixed. Perhaps
>> > we should hold off on this?
>>
>> Yes, I would like to see another solution before merging this patch.
>
> Joe, do you know whether this needs further action? It's not merged and
> I don't know whether it should be.
No, it looks like commit 76e671eade40 ("datapath: backport: vxlan:
avoid using stale vxlan socket.") in the OVS tree fixes this issue,
rendering this version of the fix unnecessary.
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