From 1bec0f05062cf21e78093b1c4a2ae744e2873b8a Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Thu, 7 Oct 2021 19:47:08 +0300 Subject: net: dsa: fix bridge_num not getting cleared after ports leaving the bridge The dp->bridge_num is zero-based, with -1 being the encoding for an invalid value. But dsa_bridge_num_put used to check for an invalid value by comparing bridge_num with 0, which is of course incorrect. The result is that the bridge_num will never get cleared by dsa_bridge_num_put, and further port joins to other bridges will get a bridge_num larger than the previous one, and once all the available bridges with TX forwarding offload supported by the hardware get exhausted, the TX forwarding offload feature is simply disabled. In the case of sja1105, 7 iterations of the loop below are enough to exhaust the TX forwarding offload bits, and further bridge joins operate without that feature. ip link add br0 type bridge vlan_filtering 1 while :; do ip link set sw0p2 master br0 && sleep 1 ip link set sw0p2 nomaster && sleep 1 done This issue is enough of an indication that having the dp->bridge_num invalid encoding be a negative number is prone to bugs, so this will be changed to a one-based value, with the dp->bridge_num of zero being the indication of no bridge. However, that is material for net-next. Fixes: f5e165e72b29 ("net: dsa: track unique bridge numbers across all DSA switch trees") Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski --- net/dsa/dsa2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/dsa/dsa2.c') diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c index b29262eee00b..6d5cc0217133 100644 --- a/net/dsa/dsa2.c +++ b/net/dsa/dsa2.c @@ -170,7 +170,7 @@ void dsa_bridge_num_put(const struct net_device *bridge_dev, int bridge_num) /* Check if the bridge is still in use, otherwise it is time * to clean it up so we can reuse this bridge_num later. */ - if (!dsa_bridge_num_find(bridge_dev)) + if (dsa_bridge_num_find(bridge_dev) < 0) clear_bit(bridge_num, &dsa_fwd_offloading_bridges); } -- cgit From 1951b3f19cfe822709c890a337906823c223c7c3 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Sat, 9 Oct 2021 15:26:07 +0300 Subject: net: dsa: hold rtnl_lock in dsa_switch_setup_tag_protocol It was a documented fact that ds->ops->change_tag_protocol() offered rtnetlink mutex protection to the switch driver, since there was an ASSERT_RTNL right before the call in dsa_switch_change_tag_proto() (initiated from sysfs). The blamed commit introduced another call path for ds->ops->change_tag_protocol() which does not hold the rtnl_mutex. This is: dsa_tree_setup -> dsa_tree_setup_switches -> dsa_switch_setup -> dsa_switch_setup_tag_protocol -> ds->ops->change_tag_protocol() -> dsa_port_setup -> dsa_slave_create -> register_netdevice(slave_dev) -> dsa_tree_setup_master -> dsa_master_setup -> dev->dsa_ptr = cpu_dp The reason why the rtnl_mutex is held in the sysfs call path is to ensure that, once the master and all the DSA interfaces are down (which is required so that no packets flow), they remain down during the tagging protocol change. The above calling order illustrates the fact that it should not be risky to change the initial tagging protocol to the one specified in the device tree at the given time: - packets cannot enter the dsa_switch_rcv() packet type handler since netdev_uses_dsa() for the master will not yet return true, since dev->dsa_ptr has not yet been populated - packets cannot enter the dsa_slave_xmit() function because no DSA interface has yet been registered So from the DSA core's perspective, holding the rtnl_mutex is indeed not necessary. Yet, drivers may need to do things which need rtnl_mutex protection. For example: felix_set_tag_protocol -> felix_setup_tag_8021q -> dsa_tag_8021q_register -> dsa_tag_8021q_setup -> dsa_tag_8021q_port_setup -> vlan_vid_add -> ASSERT_RTNL These drivers do not really have a choice to take the rtnl_mutex themselves, since in the sysfs case, the rtnl_mutex is already held. Fixes: deff710703d8 ("net: dsa: Allow default tag protocol to be overridden from DT") Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller --- net/dsa/dsa2.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net/dsa/dsa2.c') diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c index 6d5cc0217133..da18094b5a04 100644 --- a/net/dsa/dsa2.c +++ b/net/dsa/dsa2.c @@ -811,7 +811,9 @@ static int dsa_switch_setup_tag_protocol(struct dsa_switch *ds) if (!dsa_is_cpu_port(ds, port)) continue; + rtnl_lock(); err = ds->ops->change_tag_protocol(ds, port, tag_ops->proto); + rtnl_unlock(); if (err) { dev_err(ds->dev, "Unable to use tag protocol \"%s\": %pe\n", tag_ops->name, ERR_PTR(err)); -- cgit