netdev - Re: [PATCHv2 net] sctp: do not free asoc when it is already dead in sctp

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Message-Id: <20171116.104941.197762465622211317.davem@davemloft.net>
Date:   Thu, 16 Nov 2017 10:49:41 +0900 (KST)
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,
        syzkaller@...glegroups.com
Subject: Re: [PATCHv2 net] sctp: do not free asoc when it is already dead
 in sctp_sendmsg

From: Xin Long <lucien.xin@...il.com>
Date: Wed, 15 Nov 2017 16:55:54 +0800

> Now in sctp_sendmsg sctp_wait_for_sndbuf could schedule out without
> holding sock sk. It means the current asoc can be freed elsewhere,
> like when receiving an abort packet.
> 
> If the asoc is just created in sctp_sendmsg and sctp_wait_for_sndbuf
> returns err, the asoc will be freed again due to new_asoc is not nil.
> An use-after-free issue would be triggered by this.
> 
> This patch is to fix it by setting new_asoc with nil if the asoc is
> already dead when cpu schedules back, so that it will not be freed
> again in sctp_sendmsg.
> 
> v1->v2:
>   set new_asoc as nil in sctp_sendmsg instead of sctp_wait_for_sndbuf.
> 
> Suggested-by: Neil Horman <nhorman@...driver.com>
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Applied.