netdev - [PATCH v3 net] net: ipv4/ipv6 addrconf: call igmp{,6}_group

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Message-Id: <20230411144955.1604591-1-vladimir.oltean@nxp.com>
Date:   Tue, 11 Apr 2023 17:49:55 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...nel.org>,
        Ido Schimmel <idosch@...dia.com>
Subject: [PATCH v3 net] net: ipv4/ipv6 addrconf: call igmp{,6}_group_dropped() while dev is still up

ipv4 devinet calls ip_mc_down(), and ipv6 calls addrconf_ifdown(), and
both of these eventually result in calls to dev_mc_del(), either through
igmp_group_dropped() or igmp6_group_dropped().

The problem is that dev_mc_del() does call __dev_set_rx_mode(), but this
will not propagate all the way to the ndo_set_rx_mode() of the device,
because of this check:

        /* dev_open will call this function so the list will stay sane. */
        if (!(dev->flags&IFF_UP))
                return;

and the NETDEV_DOWN notifier is emitted while the interface is already
down. OTOH we have NETDEV_GOING_DOWN which is emitted a bit earlier -
see:

dev_close_many()
-> __dev_close_many()
   -> call_netdevice_notifiers(NETDEV_GOING_DOWN, dev);
   -> dev->flags &= ~IFF_UP;
-> call_netdevice_notifiers(NETDEV_DOWN, dev);

Normally this oversight is easy to miss, because the addresses aren't
lost, just not synced to the device until the next up event.

DSA does some processing in its dsa_slave_set_rx_mode(), and assumes
that all addresses that were synced are also unsynced by the time the
device is unregistered. Due to that assumption not being satisfied,
the WARN_ON(!list_empty(&dp->mdbs)); from dsa_switch_release_ports()
triggers, and we leak memory corresponding to the multicast addresses
that were never synced.

Minimal reproducer:
ip link set swp0 up
ip link set swp0 down
echo 0000:00:00.5 > /sys/bus/pci/drivers/mscc_felix/unbind

The proposal is to respond to that slightly earlier notifier with the
IGMP address deletion, so that the ndo_set_rx_mode() of the device does
actually get called.

Fixes: 5e8a1e03aa4d ("net: dsa: install secondary unicast and multicast addresses as host FDB/MDB")
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
v2->v3:
Returned to the original strategy, with Ido's modification applied
(to only touch the netdev notifier values, not the inetaddr notifier
values).

v2 at:
https://patchwork.kernel.org/project/netdevbpf/patch/20230410195220.1335670-1-vladimir.oltean@nxp.com/

 net/ipv4/devinet.c  | 2 +-
 net/ipv6/addrconf.c | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 5deac0517ef7..679c9819f25b 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1588,7 +1588,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
 		/* Send gratuitous ARP to notify of link change */
 		inetdev_send_gratuitous_arp(dev, in_dev);
 		break;
-	case NETDEV_DOWN:
+	case NETDEV_GOING_DOWN:
 		ip_mc_down(in_dev);
 		break;
 	case NETDEV_PRE_TYPE_CHANGE:
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 3797917237d0..f4a3b2693d6a 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3670,12 +3670,12 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
 		}
 		break;
 
-	case NETDEV_DOWN:
+	case NETDEV_GOING_DOWN:
 	case NETDEV_UNREGISTER:
 		/*
 		 *	Remove all addresses from this interface.
 		 */
-		addrconf_ifdown(dev, event != NETDEV_DOWN);
+		addrconf_ifdown(dev, event != NETDEV_GOING_DOWN);
 		break;
 
 	case NETDEV_CHANGENAME:
@@ -6252,7 +6252,7 @@ static void dev_disable_change(struct inet6_dev *idev)
 
 	netdev_notifier_info_init(&info, idev->dev);
 	if (idev->cnf.disable_ipv6)
-		addrconf_notify(NULL, NETDEV_DOWN, &info);
+		addrconf_notify(NULL, NETDEV_GOING_DOWN, &info);
 	else
 		addrconf_notify(NULL, NETDEV_UP, &info);
 }
-- 
2.34.1