Hi, net_device->ndo_set_rx_headroom (introduced in 871b642adebe300be2e50aa5f65a418510f636ec) says
"Setting a negative value reset the rx headroom to the default value". It seems that the OVS implementation in 3a927bc7cf9d0fbe8f4a8189dd5f8440228f64e7 overlooked this and sets dev->needed_headroom unconditionally. This doesn't have an immediate effect, but can mess up later LL_RESERVED_SPACE calculations, such as done in net/ipv6/mcast.c:mld_newpack. For reference, this issue was found from a skb_panic raised there after the length calculations had given the wrong result. Note the other current users of this interface (drives/net/tun.c:tun_set_headroom and drives/net/veth.c:veth_set_rx_headroom) are both checking this correctly and thus need no modification. An OpenStack tempest run (http://docs.openstack.org/developer/tempest/) that reliably hit this panic works correctly with this patch. Thanks to Ben for some pointers from the crash dumps! Cc: Benjamin Poirier <bpoir...@suse.com> Cc: Paolo Abeni <pab...@redhat.com> Cc: netdev@vger.kernel.org Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1361414 Signed-off-by: Ian Wienand <iwien...@redhat.com> --- net/openvswitch/vport-internal_dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c index 434e04c..f294253 100644 --- a/net/openvswitch/vport-internal_dev.c +++ b/net/openvswitch/vport-internal_dev.c @@ -140,7 +140,7 @@ internal_get_stats(struct net_device *dev, struct rtnl_link_stats64 *stats) static void internal_set_rx_headroom(struct net_device *dev, int new_hr) { - dev->needed_headroom = new_hr; + dev->needed_headroom = new_hdr < 0 ? 0 : new_hr; } static const struct net_device_ops internal_dev_netdev_ops = { -- 2.7.4
