netdev - Re: [PATCH net v2] ipv6: the entire IPv6 header chain must fit the first fragment

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Message-Id: <20180325.211803.488689473146529035.davem@davemloft.net>
Date:   Sun, 25 Mar 2018 21:18:03 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, dsahern@...il.com,
        syzbot+91e6f9932ff122fa4410@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com, eric.dumazet@...il.com
Subject: Re: [PATCH net v2] ipv6: the entire IPv6 header chain must fit the
 first fragment

From: Paolo Abeni <pabeni@...hat.com>
Date: Fri, 23 Mar 2018 14:47:30 +0100

> While building ipv6 datagram we currently allow arbitrary large
> extheaders, even beyond pmtu size. The syzbot has found a way
> to exploit the above to trigger the following splat:
 ...
> As stated by RFC 7112 section 5:
> 
>    When a host fragments an IPv6 datagram, it MUST include the entire
>    IPv6 Header Chain in the First Fragment.
> 
> So this patch addresses the issue dropping datagrams with excessive
> extheader length. It also updates the error path to report to the
> calling socket nonnegative pmtu values.
> 
> The issue apparently predates git history.
> 
> v1 -> v2: cleanup error path, as per Eric's suggestion
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzbot+91e6f9932ff122fa4410@...kaller.appspotmail.com
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied and queued up for -stable.