Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752192AbdHJLZw (ORCPT ); Thu, 10 Aug 2017 07:25:52 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:43028 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751456AbdHJLZv (ORCPT ); Thu, 10 Aug 2017 07:25:51 -0400 Date: Thu, 10 Aug 2017 14:24:51 +0300 From: Dan Carpenter To: Phil Elwell Cc: Eric Anholt , Stefan Wahren , Greg Kroah-Hartman , Florian Fainelli , Aishwarya Pant , linux-rpi-kernel@lists.infradead.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] staging: bcm2835-audio: Fix memory corruption Message-ID: <20170810112451.nkvj7p6r7qgqqnh3@mwanda> References: <1502193902-87160-1-git-send-email-phil@raspberrypi.org> <20170810102155.6j373u3yktnlwsqw@mwanda> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2783 Lines: 64 On Thu, Aug 10, 2017 at 11:52:42AM +0100, Phil Elwell wrote: > On 10/08/2017 11:21, Dan Carpenter wrote: > > The original patch did not go through the normal review process... > > > > On Tue, Aug 08, 2017 at 01:05:02PM +0100, Phil Elwell wrote: > >> I'm all for fixing memory leaks, but freeing a block while it is still > >> being used is a recipe for hard-to-debug kernel exceptions. > >> > > > > This bug completely breaks the driver doesn't it? It's not very subtle > > so it should be easy to diagnose with git bisect. > > It's more subtle than that - the failure isn't consistent, sometimes crashing > and sometimes not depending on how and when memory is reused. > > >> 1) There is already a vchi method for freeing the instance, so use it. > >> 2) Only call it on error, and then only before initted is false. > >> > >> Signed-off-by: Phil Elwell > >> Fixes: 0adbfd4694c2 ("staging: bcm2835-audio: fix memory leak in bcm2835_audio_open_connection()") > >> --- > >> drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c > >> index 5f3d8f2..89f96f3 100644 > >> --- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c > >> +++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c > >> @@ -409,6 +409,7 @@ static int bcm2835_audio_open_connection(struct bcm2835_alsa_stream *alsa_stream > >> LOG_ERR("%s: failed to connect VCHI instance (ret=%d)\n", > >> __func__, ret); > >> > >> + vchi_disconnect(vchi_instance); > > > > This is ugly because why are we calling disconnect() if connect() fails? > > These functions should be symetric so disconnect only disconnects and > > we call a different function to undo vchi_initialise(). > > Agreed - I'm not going to change the API, but I can add a comment. > Nah... Please don't do that. Just create a function: static void vchiq_free(VCHIQ_INSTANCE_T *vchi_instance) { kfree(vchi_instance); } Really vchi_initialise() is badly named and it's just a wrapper around vchiq_initialise(). It should be deleted and vchiq_initialise() should be renamed to allocate instead of initialize... But that's for a separate patch. And also we should move the kfree() out of disconnect() like I said and instead call vchiq_free(). But again, that's for a separate patch. Change the goto to "return -EIO." Leave the last error path as-is. Eventually we will want to break this into two functions, one that allocates the first vchi_instance and one that calls vc_vchi_audio_init(). But again, there are many patches needed to fix this code. regards, dan carpenter