Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752257AbdHJKwp (ORCPT ); Thu, 10 Aug 2017 06:52:45 -0400 Received: from mx08-00252a01.pphosted.com ([91.207.212.211]:59601 "EHLO mx08-00252a01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752162AbdHJKwn (ORCPT ); Thu, 10 Aug 2017 06:52:43 -0400 Subject: Re: [PATCH] staging: bcm2835-audio: Fix memory corruption To: Dan Carpenter 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 References: <1502193902-87160-1-git-send-email-phil@raspberrypi.org> <20170810102155.6j373u3yktnlwsqw@mwanda> From: Phil Elwell Message-ID: Date: Thu, 10 Aug 2017 11:52:42 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170810102155.6j373u3yktnlwsqw@mwanda> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-08-10_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_spam_notspam policy=outbound_spam score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1708100182 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2182 Lines: 53 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. >> ret = -EIO; >> goto err_free_mem; > > This label name is out of date. There is a later error path where > vc_vchi_audio_init() fails and we leak on that path. Also agreed. I'll rework it. > Also why is > vchi_instance a static variable? Arglebargleblargleblah... You may well think that. I couldn't possibly comment. Phil