netdev - Re: [PATCH net] tcp: md5: reject TCP_MD5SIG or TCP_MD5SIG

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Message-Id: <20180412.215002.623918426728104388.davem@davemloft.net>
Date:   Thu, 12 Apr 2018 21:50:02 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net] tcp: md5: reject TCP_MD5SIG or TCP_MD5SIG_EXT on
 established sockets

From: Eric Dumazet <edumazet@...gle.com>
Date: Wed, 11 Apr 2018 14:36:28 -0700

> syzbot/KMSAN reported an uninit-value in tcp_parse_options() [1]
> 
> I believe this was caused by a TCP_MD5SIG being set on live
> flow.
> 
> This is highly unexpected, since TCP option space is limited.
> 
> For instance, presence of TCP MD5 option automatically disables
> TCP TimeStamp option at SYN/SYNACK time, which we can not do
> once flow has been established.
> 
> Really, adding/deleting an MD5 key only makes sense on sockets
> in CLOSE or LISTEN state.
 ...
> Fixes: cfb6eeb4c860 ("[TCP]: MD5 Signature Option (RFC2385) support.")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable.