netdev - Re: [PATCH net-next] mptcp: fix deadlock in mptcp

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Date:   Thu, 05 May 2022 13:50:01 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Geliang Tang <geliang.tang@...e.com>
Cc:     Matthieu Baerts <matthieu.baerts@...sares.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        mptcp@...ts.linux.dev, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net-next] mptcp: fix deadlock in mptcp_close()

On Thu, 2022-05-05 at 14:03 +0300, Dan Carpenter wrote:
> The mptcp_data_lock/unlock(sk) functions are taking the same spin lock
> as the lock_sock()/release_sock() functions.  So we're already holding
> the lock at this point and taking it again will lead to a deadlock.

Note that lock_sock() (and release_sock()) releases the relevant
spinlock before completion. AFAICs the above deadlock is not possible.

Still I think we can revert commit 4293248c6704, I don't see why we
need the addtional spin lock ?!? 

Thanks!

Paolo