From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758895AbXGCUDt (ORCPT ); Tue, 3 Jul 2007 16:03:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758309AbXGCUD3 (ORCPT ); Tue, 3 Jul 2007 16:03:29 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:55828 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757998AbXGCUD2 (ORCPT ); Tue, 3 Jul 2007 16:03:28 -0400 Date: Tue, 3 Jul 2007 13:03:18 -0700 From: Andrew Morton To: Jesper Juhl Cc: Linux Kernel Mailing List , Jaroslav Kysela Subject: Re: [PATCH][isapnp] Fix a potential NULL pointer dereference in isapnp_read_tag() Message-Id: <20070703130318.9dbec3ac.akpm@linux-foundation.org> In-Reply-To: <200707010138.32075.jesper.juhl@gmail.com> References: <200707010138.32075.jesper.juhl@gmail.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 1 Jul 2007 01:38:31 +0200 Jesper Juhl wrote: > The Coverity checker spotted (as bug #809) that we dereference 'type' > long before we actually test it against NULL in > drivers/pnp/isapnp/core.c::isapnp_read_tag() - both branches of the > 'if (tag & 0x80)' dereference type, and since this 'if' is before the test > against NULL and the return of -1, this will blow up is ever type is NULL. > This is easy to fix by simply moving the NULL test to the beginning of > the function. > > > Signed-off-by: Jesper Juhl > --- > > drivers/pnp/isapnp/core.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX > diff --git a/drivers/pnp/isapnp/core.c b/drivers/pnp/isapnp/core.c > index a0b1587..5696924 100644 > --- a/drivers/pnp/isapnp/core.c > +++ b/drivers/pnp/isapnp/core.c > @@ -356,6 +356,8 @@ static int __init isapnp_read_tag(unsigned char *type, unsigned short *size) > { > unsigned char tag, tmp[2]; > > + if (!type) /* wrong type */ > + return -1; > isapnp_peek(&tag, 1); > if (tag == 0) /* invalid tag */ > return -1; > @@ -370,8 +372,6 @@ static int __init isapnp_read_tag(unsigned char *type, unsigned short *size) > #if 0 > printk(KERN_DEBUG "tag = 0x%x, type = 0x%x, size = %i\n", tag, *type, *size); > #endif > - if (type == 0) /* wrong type */ > - return -1; > if (*type == 0xff && *size == 0xffff) /* probably invalid data */ > return -1; > return 0; dood, look at the callers. NULL is not possible here.