netdev - Re: [PATCH net] net/smc: add fallback check to connect()

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Date:   Sun, 15 Dec 2019 11:15:58 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Karsten Graul <kgraul@...ux.ibm.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, heiko.carstens@...ibm.com,
        raspl@...ux.ibm.com, ubraun@...ux.ibm.com
Subject: Re: [PATCH net] net/smc: add fallback check to connect()

On Thu, 12 Dec 2019 22:35:58 +0100, Karsten Graul wrote:
> From: Ursula Braun <ubraun@...ux.ibm.com>
> 
> FASTOPEN setsockopt() or sendmsg() may switch the SMC socket to fallback
> mode. Once fallback mode is active, the native TCP socket functions are
> called. Nevertheless there is a small race window, when FASTOPEN
> setsockopt/sendmsg runs in parallel to a connect(), and switch the
> socket into fallback mode before connect() takes the sock lock.
> Make sure the SMC-specific connect setup is omitted in this case.
> 
> This way a syzbot-reported refcount problem is fixed, triggered by
> different threads running non-blocking connect() and FASTOPEN_KEY
> setsockopt.
> 
> Reported-by: syzbot+96d3f9ff6a86d37e44c8@...kaller.appspotmail.com
> Fixes: 6d6dd528d5af ("net/smc: fix refcount non-blocking connect() -part 2")
> Signed-off-by: Ursula Braun <ubraun@...ux.ibm.com>
> Signed-off-by: Karsten Graul <kgraul@...ux.ibm.com>

Applied, and queued for stable, thank you!