netdev - Re: [PATCH net 1/2] mptcp: forbit mcast-related sockopt on MPTCP sockets

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Date:   Thu, 1 Apr 2021 12:40:25 -0700 (PDT)
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     Paolo Abeni <pabeni@...hat.com>
cc:     netdev@...r.kernel.org, mptcp@...ts.linux.dev,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net 1/2] mptcp: forbit mcast-related sockopt on MPTCP
 sockets

On Thu, 1 Apr 2021, Paolo Abeni wrote:

> Unrolling mcast state at msk dismantel time is bug prone, as
> syzkaller reported:
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.11.0-syzkaller #0 Not tainted
> ------------------------------------------------------
> syz-executor905/8822 is trying to acquire lock:
> ffffffff8d678fe8 (rtnl_mutex){+.+.}-{3:3}, at: ipv6_sock_mc_close+0xd7/0x110 net/ipv6/mcast.c:323
>
> but task is already holding lock:
> ffff888024390120 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1600 [inline]
> ffff888024390120 (sk_lock-AF_INET6){+.+.}-{0:0}, at: mptcp6_release+0x57/0x130 net/mptcp/protocol.c:3507
>
> which lock already depends on the new lock.
>
> Instead we can simply forbit any mcast-related setsockopt
>
> Fixes: 717e79c867ca5 ("mptcp: Add setsockopt()/getsockopt() socket operations")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
> net/mptcp/protocol.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 45 insertions(+)
>

Thanks Paolo.

Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>

--
Mat Martineau
Intel