From: Jakub Kicinski <kuba@kernel.org>
To: Joseph Huang <Joseph.Huang@garmin.com>
Cc: "Roopa Prabhu" <roopa@nvidia.com>,
"Nikolay Aleksandrov" <nikolay@nvidia.com>,
"David S. Miller" <davem@davemloft.net>,
bridge@lists.linux-foundation.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
"Linus Lüssing" <linus.luessing@c0d3.blue>
Subject: Re: [PATCH] bridge: Fix a deadlock when enabling multicast snooping
Date: Thu, 3 Dec 2020 10:28:02 -0800 [thread overview]
Message-ID: <20201203102802.62bc86ba@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com> (raw)
In-Reply-To: <20201201214047.128948-1-Joseph.Huang@garmin.com>
On Tue, 1 Dec 2020 16:40:47 -0500 Joseph Huang wrote:
> When enabling multicast snooping, bridge module deadlocks on multicast_lock
> if 1) IPv6 is enabled, and 2) there is an existing querier on the same L2
> network.
>
> The deadlock was caused by the following sequence: While holding the lock,
> br_multicast_open calls br_multicast_join_snoopers, which eventually causes
> IP stack to (attempt to) send out a Listener Report (in igmp6_join_group).
> Since the destination Ethernet address is a multicast address, br_dev_xmit
> feeds the packet back to the bridge via br_multicast_rcv, which in turn
> calls br_multicast_add_group, which then deadlocks on multicast_lock.
>
> The fix is to move the call br_multicast_join_snoopers outside of the
> critical section. This works since br_multicast_join_snoopers only deals
> with IP and does not modify any multicast data structures of the bridge,
> so there's no need to hold the lock.
>
> Fixes: 4effd28c1245 ("bridge: join all-snoopers multicast address")
>
> Signed-off-by: Joseph Huang <Joseph.Huang@garmin.com>
Nik, Linus - how does this one look?
next prev parent reply other threads:[~2020-12-03 18:29 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 21:40 [PATCH] bridge: Fix a deadlock when enabling multicast snooping Joseph Huang
2020-12-03 18:28 ` Jakub Kicinski [this message]
2020-12-03 20:46 ` Nikolay Aleksandrov
2020-12-03 21:53 ` Huang, Joseph
2020-12-03 22:42 ` Huang, Joseph
2020-12-03 23:34 ` Nikolay Aleksandrov
2020-12-04 21:39 ` [PATCH v2] " Joseph Huang
2020-12-04 22:11 ` Nikolay Aleksandrov
2020-12-04 22:30 ` Huang, Joseph
2020-12-04 23:56 ` [PATCH v3] " Joseph Huang
2020-12-05 8:56 ` Nikolay Aleksandrov
2020-12-08 1:20 ` Jakub Kicinski
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