From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mg.richtek.com (mg.richtek.com [220.130.44.152]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 36E988472; Fri, 17 May 2024 06:32:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.130.44.152 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715927534; cv=none; b=BCXxgsquqE0g44NHfOw+MDAPhV27R2R6yx7jmRcmXkVUFMFF1/73i1BGD+2VEvKAOnnT8O7YawGKuBBQMOY17CGXxYhiKHElQu6UZnd5mvu/Je1ltTYiNl9rUrojZ0lPXcHH1GLPboVX3B8M0WiSPGiI/WfvmI3vSFmZGHuUuJg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715927534; c=relaxed/simple; bh=SAb9BPrFdCY6bm78BVJ5rnJLzeV2qvsVCBYu6rx2eq4=; h=Date:From:To:CC:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WmWOC0x+c/ECEfEGKOBUqN/9wvR1hQo72wOupC70bNHiGnaFTNT0bCLoCNc6jKHSeZ72SIrNt0Ajxt+87O3QFCkKO5Angh9bTL3bW+dCq31xAOQO61894wPmO4pLG9xhjbq2+w+O1KYye/s0fOZOn5wXsxaO2Yybju6F6lSyWps= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=richtek.com; spf=pass smtp.mailfrom=richtek.com; dkim=pass (2048-bit key) header.d=richtek.com header.i=@richtek.com header.b=OcB2CdCM; arc=none smtp.client-ip=220.130.44.152 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=richtek.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=richtek.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=richtek.com header.i=@richtek.com header.b="OcB2CdCM" X-MailGates: (SIP:2,PASS,NONE)(compute_score:DELIVER,40,3) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=richtek.com; s=richtek; t=1715927528; bh=+tnHjAdOwn7MTvQ9Izy5ZraLSNprRXQmhSoT/2DAs2U=; l=3581; h=Date:From:To:Subject:Message-ID:MIME-Version; b=OcB2CdCM3Q2KLqdKTI/5YvcUYvx+1AmRoZ5uqDDtoYGMDU8KgxcUnO0USl90U22Eh v/bYFrW9wfaQFMgzOmR7CvgihC2U2s+6e96385J02T9fZCjvegWL3zZiXzR4aW0I9k wLdQR7apFBu33YENd6r6s2MOJlCwXzk8buPflw0PH7+eWZXiC79LpYGmddAerXDxRE 20mXdZ+yyXbSIbpal4fHv+Ig870lSvzQDQn3umwhjzaU+uNiK1JDmB3zmHcVlTlIme x5rM6cXdrZLrbnHTu0GWQF5v8fQYpwIg6Mpno2DhCjHjxIcwymoqUtOn29uQF95EOB 8Ab+bj/HG6b+A== Received: from 192.168.10.46 by mg.richtek.com with MailGates ESMTPS Server V6.0(3213210:0:AUTH_RELAY) (envelope-from ) (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256/256); Fri, 17 May 2024 14:31:50 +0800 (CST) Received: from ex4.rt.l (192.168.10.47) by ex3.rt.l (192.168.10.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.4; Fri, 17 May 2024 14:31:50 +0800 Received: from linuxcarl2.richtek.com (192.168.10.154) by ex4.rt.l (192.168.10.45) with Microsoft SMTP Server id 15.2.1544.4 via Frontend Transport; Fri, 17 May 2024 14:31:50 +0800 Date: Fri, 17 May 2024 14:31:50 +0800 From: ChiYuan Huang To: Sakari Ailus CC: Mauro Carvalho Chehab , Daniel Scally , Laurent Pinchart , Jean-Michel Hautbois , , Subject: Re: [PATCH] media: v4l: async: Fix NULL pointer when v4l2 flash subdev binding Message-ID: <20240517063150.GA12245@linuxcarl2.richtek.com> References: Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Hi, Sakari: Thanks for your reply. If any misunderstanding, please correct me. On Thu, May 16, 2024 at 10:42:05AM +0000, Sakari Ailus wrote: > Hi Chi Yuan, > > On Wed, May 08, 2024 at 10:51:49AM +0800, cy_huang@richtek.com wrote: > > From: ChiYuan Huang > > > > In v4l2_async_create_ancillary_links(), if v4l2 async notifier is > > created from v4l2 device, the v4l2 flash subdev async binding will enter > > the logic to create media link. Due to the subdev of notifier is NULL, > > this will cause NULL pointer to access the subdev entity. Therefore, add > > the check to bypass it. > > > > Fixes: aa4faf6eb271 ("media: v4l2-async: Create links during v4l2_async_match_notify()") > > Signed-off-by: ChiYuan Huang > > --- > > Hi, > > > > I'm trying to bind the v4l2 subdev for flashlight testing. It seems > > some logic in v4l2 asynd binding is incorrect. > > > > From the change, I modified vim2m as the test driver to bind mt6370 flashlight. > > > > Here's the backtrace log. > > > > vim2m soc:vim2m: bound [white:flash-2] > > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058 > > ......skipping > > Call trace: > > media_create_ancillary_link+0x48/0xd8 [mc] > > v4l2_async_match_notify+0x17c/0x208 [v4l2_async] > > v4l2_async_register_subdev+0xb8/0x1d0 [v4l2_async] > > There's something wrong obviously somewhere but wherea? > In vim2m driver, I added v4l2_async_nf_init -> v4l2_async_nf_add_fwnode_remote -> v4l2_async_nf_register. >From the async flow, in notifier complete ops to create v4l-subdevX node for the specified subdev. > A sub-notifier does have a sub-device after the notifier initialisation. Why? Are you saying to the notifier can only be used for subdev and subdev binding, not v4l2 and subdev binding? But to create v4l-subdevX, the key is only v4l2 device and its needed subdev. > Maybe the initialisation does not happen in the right order? AFAIK, Async flow can solve the probe order and makes the user no need to care the probe order. >From the stacktrace, I'm pretty sure it's not the probe order issue. > > > __v4l2_flash_init.part.0+0x3b4/0x4b0 [v4l2_flash_led_class] > > v4l2_flash_init+0x28/0x48 [v4l2_flash_led_class] > > mt6370_led_probe+0x348/0x690 [leds_mt6370_flash] > > > > After tracing the code, it will let the subdev labeled as F_LENS or > > F_FLASH function to create media link. To prevent the NULL pointer > > issue, the simplest way is add a check when 'n->sd' is NULL and bypass > > the later media link creataion. > > --- > > drivers/media/v4l2-core/v4l2-async.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c > > index 3ec323bd528b..9d3161c51954 100644 > > --- a/drivers/media/v4l2-core/v4l2-async.c > > +++ b/drivers/media/v4l2-core/v4l2-async.c > > @@ -324,6 +324,9 @@ static int v4l2_async_create_ancillary_links(struct v4l2_async_notifier *n, > > sd->entity.function != MEDIA_ENT_F_FLASH) > > return 0; > > > > + if (!n->sd) > > + return 0; > > This isn't the right fix: the ancillary link won't be created as a result. > Due to the notifier is created by v4l2 device not subdev, this 'n->sd' is NULL. The NULL 'n->sd' will be referenced by the next flow 'media_create_ancillary_link'. Or is it caused by the wrong usage? > > + > > link = media_create_ancillary_link(&n->sd->entity, &sd->entity); > > > > #endif > > -- > Regards, > > Sakari Ailus