From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with archive (Exim 4.43)
	id 1KCcIO-0004Wn-BK
	for mharc-grub-devel@gnu.org; Sat, 28 Jun 2008 11:25:00 -0400
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1KCcIM-0004TJ-Mt
	for grub-devel@gnu.org; Sat, 28 Jun 2008 11:24:58 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1KCcIL-0004Qa-AK
	for grub-devel@gnu.org; Sat, 28 Jun 2008 11:24:58 -0400
Received: from [199.232.76.173] (port=54295 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1KCcIL-0004QB-0U
	for grub-devel@gnu.org; Sat, 28 Jun 2008 11:24:57 -0400
Received: from mta-out.inet.fi ([195.156.147.13]:41090
	helo=kirsi2.rokki.sonera.fi)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <chaac@nic.fi>) id 1KCcIK-0007Js-KS
	for grub-devel@gnu.org; Sat, 28 Jun 2008 11:24:56 -0400
Received: from [127.0.0.1] (88.193.32.97) by kirsi2.rokki.sonera.fi (8.5.014)
	id 4858893A006B975F for grub-devel@gnu.org;
	Sat, 28 Jun 2008 18:24:54 +0300
Message-ID: <486657CD.9000506@nic.fi>
Date: Sat, 28 Jun 2008 18:25:01 +0300
From: =?ISO-8859-1?Q?Vesa_J=E4=E4skel=E4inen?= <chaac@nic.fi>
User-Agent: Thunderbird 2.0.0.14 (Windows/20080421)
MIME-Version: 1.0
To: The development of GRUB 2 <grub-devel@gnu.org>
References: <20080628080344.76c766f8@gibibit.com>
In-Reply-To: <20080628080344.76c766f8@gibibit.com>
X-Enigmail-Version: 0.95.6
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-detected-kernel: by monty-python.gnu.org: Linux 2.6 (newer, 3)
Subject: Re: grub_strdup() error; or: grub_malloc() zeroes memory?
X-BeenThere: grub-devel@gnu.org
X-Mailman-Version: 2.1.5
Precedence: list
Reply-To: The development of GRUB 2 <grub-devel@gnu.org>
List-Id: The development of GRUB 2 <grub-devel.gnu.org>
List-Unsubscribe: <http://lists.gnu.org/mailman/listinfo/grub-devel>,
	<mailto:grub-devel-request@gnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/grub-devel>
List-Post: <mailto:grub-devel@gnu.org>
List-Help: <mailto:grub-devel-request@gnu.org?subject=help>
List-Subscribe: <http://lists.gnu.org/mailman/listinfo/grub-devel>,
	<mailto:grub-devel-request@gnu.org?subject=subscribe>
X-List-Received-Date: Sat, 28 Jun 2008 15:24:58 -0000

Colin D Bennett wrote:
> It looks like grub_strdup() does not terminate the returned string with
> a 0 byte.  The only way I could see it working is if grub_malloc()
> filled the returned memory with zeroes.  Does it?
> 
> From kern/misc.c: (circa line 476)
> 
>    char *
>    grub_strdup (const char *s)
>    {
>      grub_size_t len;
>      char *p;
>      
>      len = grub_strlen (s) + 1;
>      p = (char *) grub_malloc (len);
>      if (! p)
>        return 0;
> 
>      return grub_memcpy (p, s, len);
>    }

Zero is copied from source string... notice strlen() + 1.

> But right after that, we have
> 
>    char *
>    grub_strndup (const char *s, grub_size_t n)
>    {
>      grub_size_t len;
>      char *p;
>      
>      len = grub_strlen (s);
>      if (len > n)
>        len = n;
>      p = (char *) grub_malloc (len + 1);
>      if (! p)
>        return 0;
>      
>      grub_memcpy (p, s, len);
>      p[len] = '\0';
>      return p;
>    }
> 
> which explicitly stores a terminating null byte.  If grub_malloc() did
> initialize the memory to zero, then this explicity store would be
> unnecessary.

Here if string is not fully copied there needs to be NUL terminator.