From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dan Carpenter <error27@gmail.com>
Date: Mon, 22 Mar 2010 12:56:26 +0000
Subject: Re: [patch] afs: potential null dereference
Message-Id: <20100322125626.GM21571@bicker>
List-Id: <kernel-janitors.vger.kernel.org>
References: <20100320111938.GT5331@bicker> <28809.1269259520@redhat.com>
In-Reply-To: <28809.1269259520@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: David Howells <dhowells@redhat.com>
Cc: kernel-janitors@vger.kernel.org, linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org

On Mon, Mar 22, 2010 at 12:05:20PM +0000, David Howells wrote:
> Dan Carpenter <error27@gmail.com> wrote:
> 
> > It seems clear from the surrounding code that xpermits is allowed to be 
> > NULL here.
> 
> Interesting.  The memcpy() won't oops due to this because if it is given a
> NULL pointer, it will also be given a zero count.  I wonder if this means the
> if-statement your patch adds is actually unnecessary...
> 

I was concerned about the dereference here:

+       if (xpermits)
+               memcpy(permits->permits, xpermits->permits,
                                         ^^^^^^^^^^^^^^^^^
+                       count * sizeof(struct afs_permit));

This code has been there for three years, so yeah, you would think if it
were a problem someone would have complained.  My theory was "xpermits"
was almost always non-null.

regards,
dan carpenter

> David