Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754729Ab0BXBCz (ORCPT ); Tue, 23 Feb 2010 20:02:55 -0500 Received: from ozlabs.org ([203.10.76.45]:47448 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754583Ab0BXBCy convert rfc822-to-8bit (ORCPT ); Tue, 23 Feb 2010 20:02:54 -0500 From: Rusty Russell To: =?utf-8?q?Am=C3=A9rico_Wang?= Subject: Re: [RESEND PATCH] module param_call: fix potential NULL pointer dereference Date: Wed, 24 Feb 2010 11:31:16 +1030 User-Agent: KMail/1.12.2 (Linux/2.6.31-19-generic; KDE/4.3.2; i686; ; ) Cc: Dongdong Deng , linux-kernel@vger.kernel.org, Andrew Morton References: <1266835251-15457-1-git-send-email-dongdong.deng@windriver.com> <201002231426.45886.rusty@rustcorp.com.au> <20100223154519.GA4779@hack> In-Reply-To: <20100223154519.GA4779@hack> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Message-Id: <201002241131.16766.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2643 Lines: 66 On Wed, 24 Feb 2010 02:15:19 am Américo Wang wrote: > On Tue, Feb 23, 2010 at 02:26:45PM +1030, Rusty Russell wrote: > >On Mon, 22 Feb 2010 09:10:51 pm Dongdong Deng wrote: > >> The param_set_fn() function will get a parameter which is a NULL > >> pointer when insmod module via bare params as following method: > >> > >> $insmod foo.ko foo > >> > >> If the param_set_fn() function didn't check that parameter and used > >> it directly, it could caused an OOPS due to NULL pointer dereference. > >> > >> The solution is simple: > >> Using "" to replace NULL parameter, thereby the param_set_fn() > >> function will never get a NULL pointer. > > > >This changes the value of booleans, and loses checking for int params, etc. > > > >I liked Americo's approach; I've combined the two approaches below. > > > >Since I'm going away, can Andrew take this? > > > >Subject: params: don't hand NULL values to param.set callbacks. > > > >An audit by Dongdong Deng revealed that most driver-author-written param > >calls don't handle val == NULL (which happens when parameters are specified > >with no =, eg "foo" instead of "foo=1"). > > > >The only real case to use this is boolean, so handle it specially for that > >case and remove a source of bugs for everyone else as suggested by Americo. > > > >Signed-off-by: Rusty Russell > >Cc: Dongdong Deng > >Cc: Américo Wang > > > >diff --git a/kernel/params.c b/kernel/params.c > >--- a/kernel/params.c > >+++ b/kernel/params.c > >@@ -59,6 +59,9 @@ static int parse_one(char *param, > > /* Find parameter */ > > for (i = 0; i < num_params; i++) { > > if (parameq(param, params[i].name)) { > >+ /* Noone handled NULL, so do it here. */ > >+ if (!val && params[i].set != param_set_bool) > >+ return -EINVAL; > > Sorry, after rethinking about this, I think it might be wrong. > > With this patch, when I use non-standard bool functions, I will not > have a chance to use '!val' which should be valid for all bool > functions. Or am I missing something? Sure, at that point we'd need something more sophisticated. But to fix this properly we want a flags word, and thus something like this which I worked on earlier: http://ozlabs.org/~rusty/kernel/rr-latest/param:param_ops.patch Cheers, Rusty. -- Away travelling 25Feb-26Mar (6 .de + 1 .pl + 17 .lt + 2 .sg) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/