linux-kernel - Re: [PATCH net] rxrpc: Fix several cases where a padded len isn't checked in ticket decode

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Date:   Thu, 15 Jun 2017 14:27:34 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     dhowells@...hat.com
Cc:     netdev@...r.kernel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] rxrpc: Fix several cases where a padded len isn't
 checked in ticket decode

From: David Howells <dhowells@...hat.com>
Date: Thu, 15 Jun 2017 00:12:24 +0100

> This fixes CVE-2017-7482.
> 
> When a kerberos 5 ticket is being decoded so that it can be loaded into an
> rxrpc-type key, there are several places in which the length of a
> variable-length field is checked to make sure that it's not going to
> overrun the available data - but the data is padded to the nearest
> four-byte boundary and the code doesn't check for this extra.  This could
> lead to the size-remaining variable wrapping and the data pointer going
> over the end of the buffer.
> 
> Fix this by making the various variable-length data checks use the padded
> length.
> 
> Reported-by: 石磊 <shilei-c@....cn>
> Signed-off-by: David Howells <dhowells@...hat.com>
> Reviewed-by: Marc Dionne <marc.c.dionne@...istor.com>
> Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>

Applied, thanks David.