From: Ian Abbott <abbotti@mev.co.uk>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Xi Wang <xi.wang@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
Mori Hess <fmhess@users.sourceforge.net>,
"security@kernel.org" <security@kernel.org>,
Lucas De Marchi <lucas.demarchi@profusion.mobi>,
Greg Kroah-Hartman <gregkh@suse.de>,
Ian Abbott <ian.abbott@mev.co.uk>,
Franky Lin <frankyl@broadcom.com>,
Greg Dietsche <Gregory.Dietsche@cuw.edu>,
Mark Pearson <markpearson_de@yahoo.de>
Subject: Re: [PATCH] comedi: integer overflow in do_insnlist_ioctl()
Date: Wed, 23 Nov 2011 16:06:25 +0000 [thread overview]
Message-ID: <4ECD1A01.3060503@mev.co.uk> (raw)
In-Reply-To: <20111123145020.GA3258@mwanda>
On 2011-11-23 14:50, Dan Carpenter wrote:
> On Wed, Nov 23, 2011 at 08:59:52AM -0500, Xi Wang wrote:
>> Thanks for the pointer. However you cannot do the overflow check using
>>
>> if (sizeof(struct comedi_insn) * insnlist.n_insns < insnlist.n_insns)
>>
>> Let's assume 32-bit system, sizeof(struct comedi_insn) = 32, and
>> insnlist.n_insns = 0x7fffffff.
>>
>> Note that 32 * 0x7fffffff = 0xffffffe0 overflows but bypasses your check.
>>
>
> Argh... You're right, my check is wrong. What I like about my patch
> though is that it doesn't introduce an arbitrary limit. Could you
> redo your check without the MAX_INSNS?
Could use something like:
if (insnlist.n_insns <= ULONG_MAX / sizeof(struct comedi_insn))
insns =
kmalloc(sizeof(struct comedi_insn) * insnlist.n_insns,
GFP_KERNEL);
if (!insns)
...
(note that insns is initialized to NULL).
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@mev.co.uk> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
next prev parent reply other threads:[~2011-11-23 16:15 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-23 0:49 [PATCH] comedi: integer overflow in do_insnlist_ioctl() Xi Wang
2011-11-23 6:13 ` Dan Carpenter
2011-11-23 13:59 ` Xi Wang
2011-11-23 14:50 ` Dan Carpenter
2011-11-23 16:06 ` Ian Abbott [this message]
2011-11-23 16:53 ` [PATCH v2] " Xi Wang
2011-11-23 21:41 ` [PATCH] " Lars-Peter Clausen
2011-11-23 21:51 ` Dan Carpenter
2011-11-24 19:07 ` Xi Wang
2011-11-25 7:25 ` Dan Carpenter
2011-11-25 21:46 ` [PATCH v3] " Xi Wang
2011-11-27 2:52 ` Greg KH
2011-11-27 11:25 ` Dan Carpenter
2011-11-27 21:24 ` Greg KH
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