netdev - possible kernel oops from user MSS

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Message-ID: <AANLkTimMDMb74-3E9vhFxZ5Dgeuk3HMzPZVjwCj+yFEJ@mail.gmail.com>
Date:	Wed, 10 Nov 2010 07:24:51 -0600
From:	Steve Chen <schen@...sta.com>
To:	netdev@...r.kernel.org
Subject: possible kernel oops from user MSS

Hello

With commit f5fff5dc8a7a3f395b0525c02ba92c95d42b7390, a user program
can pass in TCP_MAXSEG of 12 (or TCPOLEN_TSTAMP_ALIGNED), and cause
kernel oops with division by 0
 in tcp_select_initial_window.  One way to prevent it is to change the
minimum value for TCP_MAXSEG in do_tcp_setsockopt from 8 to some value
over 12.  Two questions.

1.  Is this the right solution?
2.  If it is, what is a good minimum value?

Thanks,

Steve
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