Re: [PATCH] media: rc: ir-lirc-codec: fix potential integer overflow

[Jarod Wilson]

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@xxxxxxxxxx

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/