From: Ido Schimmel <idosch@nvidia.com>
To: Nikolay Aleksandrov <razor@blackwall.org>
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, horms@kernel.org,
tobias@waldekranz.com, bridge@lists.linux.dev
Subject: Re: [PATCH net] net: bridge: mst: move switchdev call outside rcu
Date: Mon, 14 Sep 2026 09:15:48 +0300 [thread overview]
Message-ID: <20260914061548.GA132848@shredder> (raw)
In-Reply-To: <20260911105021.1385934-1-razor@blackwall.org>
On Fri, Sep 11, 2026 at 01:50:21PM +0300, Nikolay Aleksandrov wrote:
> This is a follow-up of one of sashiko's pre-existing bug reports.
> br_mst_set_state() calls switchdev_port_attr_set() for nonzero MSTIs
> while holding rcu_read_lock() which invokes the blocking switchdev
> notifier chain and may sleep. Nonzero MSTI changes come from netlink
> with rtnl held. Move the switchdev call before entering the rcu section and
> assert that rtnl is held.
>
> The call cannot be deferred because netlink needs its error and extack.
> Also DSA reads the old bridge MST state during the callback and checks it.
> A deferred callback will be late and will see the updated state.
>
> Fixes: 7ae9147f4312 ("net: bridge: mst: Notify switchdev drivers of MST state changes")
Nit: blaming 3a7c1661ae13 ("net: bridge: mst: fix vlan use-after-free")
would be more accurate, but in practice it doesn't matter since this
commit blamed ec7328b59176 that is present in the same release as
7ae9147f4312.
> Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
next prev parent reply other threads:[~2026-09-14 6:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-11 10:50 [PATCH net] net: bridge: mst: move switchdev call outside rcu Nikolay Aleksandrov
2026-09-14 6:15 ` Ido Schimmel [this message]
2026-09-15 10:23 ` Paolo Abeni
2026-09-15 10:25 ` Nikolay Aleksandrov
2026-09-15 10:26 ` Nikolay Aleksandrov
2026-09-15 10:30 ` patchwork-bot+netdevbpf
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