From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarod Wilson Date: Thu, 02 Dec 2010 15:00:45 +0000 Subject: Re: [PATCH] media: rc: ir-lirc-codec: fix potential integer overflow Message-Id: <20101202150045.GA32168@redhat.com> List-Id: References: <20101202045126.GA1784@bicker> In-Reply-To: <20101202045126.GA1784@bicker> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dan Carpenter , Vasiliy Kulikov , kernel-janitors@vger.kernel.org, Mauro Carvalho Chehab , David =?iso-8859-1?Q?H=E4rdeman?= , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org On Thu, Dec 02, 2010 at 07:51:26AM +0300, Dan Carpenter wrote: > On Fri, Nov 26, 2010 at 08:06:35PM +0300, Vasiliy Kulikov wrote: > > count = n / sizeof(int); > > - if (count > LIRCBUF_SIZE || count % 2 = 0) > > + if (count > LIRCBUF_SIZE || count % 2 = 0 || n % sizeof(int) != 0) > ^^^^^^^^^^^^^^^^^^^^ > > Wait, what? We just checked this a couple lines before. Bah. I'd only looked at the diff, which didn't have enough context. I thought that looked familiar. Indeed, this part seems to be unnecessary. > The rest of the patch is right and a clever catch. It would affect > x86_64 systems and not i386. This doesn't have security implications > does it? You'd just catch the kmalloc() stack trace for insanely large > allocations. Even on x86_64, it looks to my (relatively untrained) eye like you'd actually be fine. n is a size_t (so, 64-bit on x86_64). count is an int (so 32-bit on x86_64). We initialize count to some 64-bit value / 4, so at most, 16 bits, which always fits just fine in the 32-bit int, no? -- Jarod Wilson jarod@redhat.com