netdev - Re: [PATCH net] sctp: hold transport before accessing its asoc in sctp_transport_get

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Message-Id: <20180827.151352.1790869499011600822.davem@davemloft.net>
Date:   Mon, 27 Aug 2018 15:13:52 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     lucien.xin@...il.com
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        marcelo.leitner@...il.com, nhorman@...driver.com
Subject: Re: [PATCH net] sctp: hold transport before accessing its asoc in
 sctp_transport_get_next

From: Xin Long <lucien.xin@...il.com>
Date: Mon, 27 Aug 2018 18:38:31 +0800

> As Marcelo noticed, in sctp_transport_get_next, it is iterating over
> transports but then also accessing the association directly, without
> checking any refcnts before that, which can cause an use-after-free
> Read.
> 
> So fix it by holding transport before accessing the association. With
> that, sctp_transport_hold calls can be removed in the later places.
> 
> Fixes: 626d16f50f39 ("sctp: export some apis or variables for sctp_diag and reuse some for proc")
> Reported-by: syzbot+fe62a0c9aa6a85c6de16@...kaller.appspotmail.com
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Applied and queued up for -stable.