netdev - Re: [PATCH net-next] mptcp: fix infinite loop on recvmsg()/worker() race.

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Message-ID: <20201008172823.3e1ea388@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 8 Oct 2020 17:28:23 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        mptcp@...ts.01.org
Subject: Re: [PATCH net-next] mptcp: fix infinite loop on recvmsg()/worker()
 race.

On Tue,  6 Oct 2020 08:27:34 +0200 Paolo Abeni wrote:
> If recvmsg() and the workqueue race to dequeue the data
> pending on some subflow, the current mapping for such
> subflow covers several skbs and some of them have not
> reached yet the received, either the worker or recvmsg()
> can find a subflow with the data_avail flag set - since
> the current mapping is valid and in sequence - but no
> skbs in the receive queue - since the other entity just
> processed them.
> 
> The above will lead to an unbounded loop in __mptcp_move_skbs()
> and a subsequent hang of any task trying to acquiring the msk
> socket lock.
> 
> This change addresses the issue stopping the __mptcp_move_skbs()
> loop as soon as we detect the above race (empty receive queue
> with data_avail set).

Applied, thanks!