The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Thanks, Sasha

------------------ original commit in Linus's tree ------------------

From 6ab4c3117aec4e08007d9e971fa4133e1de1082d Mon Sep 17 00:00:00 2001

From: Vladimir Oltean vladimir.oltean@nxp.com Date: Mon, 22 Mar 2021 20:21:08 +0200 Subject: [PATCH] net: bridge: don't notify switchdev for local FDB addresses

As explained in this discussion: https://lore.kernel.org/netdev/20210117193009.io3nungdwuzmo5f7@skbuf/

the switchdev notifiers for FDB entries managed to have a zero-day bug. The bridge would not say that this entry is local:

ip link add br0 type bridge ip link set swp0 master br0 bridge fdb add dev swp0 00:01:02:03:04:05 master local

and the switchdev driver would be more than happy to offload it as a normal static FDB entry. This is despite the fact that 'local' and non-'local' entries have completely opposite directions: a local entry is locally terminated and not forwarded, whereas a static entry is forwarded and not locally terminated. So, for example, DSA would install this entry on swp0 instead of installing it on the CPU port as it should.

There is an even sadder part, which is that the 'local' flag is implicit if 'static' is not specified, meaning that this command produces the same result of adding a 'local' entry:

bridge fdb add dev swp0 00:01:02:03:04:05 master

I've updated the man pages for 'bridge', and after reading it now, it should be pretty clear to any user that the commands above were broken and should have never resulted in the 00:01:02:03:04:05 address being forwarded (this behavior is coherent with non-switchdev interfaces): https://patchwork.kernel.org/project/netdevbpf/cover/20210211104502.2081443-... If you're a user reading this and this is what you want, just use:

bridge fdb add dev swp0 00:01:02:03:04:05 master static

Because switchdev should have given drivers the means from day one to classify FDB entries as local/non-local, but didn't, it means that all drivers are currently broken. So we can just as well omit the switchdev notifications for local FDB entries, which is exactly what this patch does to close the bug in stable trees. For further development work where drivers might want to trap the local FDB entries to the host, we can add a 'bool is_local' to br_switchdev_fdb_call_notifiers(), and selectively make drivers act upon that bit, while all the others ignore those entries if the 'is_local' bit is set.

Fixes: 6b26b51b1d13 ("net: bridge: Add support for notifying devices about FDB add/del") Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Signed-off-by: David S. Miller davem@davemloft.net --- net/bridge/br_switchdev.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c index b89503832fcc..1e24d9a2c9a7 100644 --- a/net/bridge/br_switchdev.c +++ b/net/bridge/br_switchdev.c @@ -128,6 +128,8 @@ br_switchdev_fdb_notify(const struct net_bridge_fdb_entry *fdb, int type) { if (!fdb->dst) return; + if (test_bit(BR_FDB_LOCAL, &fdb->flags)) + return;

switch (type) { case RTM_DELNEIGH: