netdev - RE: [patch added to 3.12-stable] net: sctp, forbid negative length

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Date:   Thu, 24 Nov 2016 12:51:05 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Jiri Slaby' <jslaby@...e.cz>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Vlad Yasevich <vyasevich@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [patch added to 3.12-stable] net: sctp, forbid negative length

From: Jiri Slaby
> Sent: 24 November 2016 09:18
> This patch has been added to the 3.12 stable tree. If you have any
> objections, please let us know.
> 
> ===============
> 
> [ Upstream commit a4b8e71b05c27bae6bad3bdecddbc6b68a3ad8cf ]
> 
> Most of getsockopt handlers in net/sctp/socket.c check len against
> sizeof some structure like:
>         if (len < sizeof(int))
>                 return -EINVAL;
> 
> On the first look, the check seems to be correct. But since len is int
> and sizeof returns size_t, int gets promoted to unsigned size_t too. So
> the test returns false for negative lengths. Yes, (-1 < sizeof(long)) is
> false.

Would it be worth adding the check in the generic setsockopt/getsockopt system
call code instead of in each and every protocol?
(Clearly for net-next, not stable.)

	David