Date: Sat, 21 Apr 2012 18:12:35 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Julia Lawall <julia.lawall@lip6.fr>
Cc: Kalle Valo <kvalo@adurom.com>,
	Julian Calaby <julian.calaby@gmail.com>,
	"John W. Linville" <linville@tuxdriver.com>,
	linux-wireless@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [patch] wireless: at76c50x: allocating too much data
Message-ID: <20120421151235.GM27101@mwanda> (sfid-20120421_171054_824118_1869D4BE)
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On Sat, Apr 21, 2012 at 05:51:41PM +0300, Dan Carpenter wrote:
> On Sat, Apr 21, 2012 at 03:51:44PM +0200, Julia Lawall wrote:
> > Looking for x = ... sizeof(x) ... I get 9 reports.  In most cases it
> > looks like sizeof(x) is coincidentally the same as the size that is
> > wanted.  Two cases that look like they could have some noticible
> > effect are:
> > 
> > arch/xtensa/platforms/iss/network.c, line 789
> > drivers/block/cciss.c, line 4211
> > 
> 
> Clever.  You'd need to restrict it to places where x was a  pointer.
> That's better than my check which was specific to kmalloc().  (So
> uh...  I'm going to rewrite mine as well to be more generic.  :P)
> 

Hm...  Smatch is not really the right tool here.  By the time Sparse
gives you the sizeof(foo) information, it just looks like a number
8.

I hacked up Sparse a bit so it works for simple expressions which
are one token in from the c tokenizer.  So:

	foo = kmalloc(sizeof(foo), GFP_KERNEL); => error.
	foo->bar = kmalloc(sizeof(foo->bar), GFP_KERNEL); => tricky.

It's not ideal.  Coccinelle is better for this.

regards,
dan carpenter