Return-path: Received: from mail-la0-f51.google.com ([209.85.215.51]:56621 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753379Ab3AGDDc (ORCPT ); Sun, 6 Jan 2013 22:03:32 -0500 MIME-Version: 1.0 In-Reply-To: <20130107024827.GZ27530@wantstofly.org> References: <1357522042-39255-1-git-send-email-nickolai@csail.mit.edu> <20130107024827.GZ27530@wantstofly.org> From: Julian Calaby Date: Mon, 7 Jan 2013 14:03:10 +1100 Message-ID: (sfid-20130107_040347_969951_9E953170) Subject: Re: [PATCH] drivers/net/wireless/mwl8k.c: avoid use-after-free To: Lennert Buytenhek Cc: Nickolai Zeldovich , "John W. Linville" , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi Lennert, On Mon, Jan 7, 2013 at 1:48 PM, Lennert Buytenhek wrote: > On Sun, Jan 06, 2013 at 08:27:22PM -0500, Nickolai Zeldovich wrote: > >> Do not dereference p->station_id after kfree(cmd) because p >> points into the cmd data structure. > > Good catch, but the patch would be better titled "mwl8k.c: avoid > having a working driver", as the station_id return code _is_ needed > by the caller in case of success. Are you sure? >> diff --git a/drivers/net/wireless/mwl8k.c b/drivers/net/wireless/mwl8k.c >> index f221b95..83564d3 100644 >> --- a/drivers/net/wireless/mwl8k.c >> +++ b/drivers/net/wireless/mwl8k.c >> @@ -4250,9 +4250,11 @@ static int mwl8k_cmd_update_stadb_add(struct ieee80211_hw *hw, >> p->amsdu_enabled = 0; >> >> rc = mwl8k_post_cmd(hw, &cmd->header); >> + if (!rc) >> + rc = p->station_id; >> kfree(cmd); >> >> - return rc ? rc : p->station_id; If I'm reading this right, the removed line is equivalent to: if( rc ) return rc; else return p->station_id; which is equivalent to: if( !rc ) rc = p->station_id; return rc; Thanks, -- Julian Calaby Email: julian.calaby@gmail.com Profile: http://www.google.com/profiles/julian.calaby/ .Plan: http://sites.google.com/site/juliancalaby/