From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 57C733F8D6; Fri, 17 May 2024 11:19:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715944798; cv=none; b=SW0s5k9pEs4SirUFbkCLbL9upqW9iVMs7khhoMLW8AI53ICGZOLnrX+ov3gRSx0WrgC4vjey5HwEktXrH5a5a2+dhz4uVcGjw3VC2h1YVQywQmikMrHDN9gCDtmKTr53JJ7K42V5dl2+2YzrxW8TJUR7lMliTCAjn4gbjB9FDHo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715944798; c=relaxed/simple; bh=bVBSHHTwjk7r5Ay2aMI6ZrBecR5S06CsKavj2yj6LG0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ghX75+kf1sCb9Qtm8jCY9IZx6gSWwZNHXbBaf+3pUDPccY1frV5g8GVW6yjNzBLvLc/nTtrju8su3aoWsIwgALkfkKq3Pd7xAdIE2lvmJzi/RYENTkxPqsxpJ/7EayCCoHYKX73RxBXXFXSdaxkzA3erB5b6avbwlIo416Lpxpg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=Corjv+R+; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="Corjv+R+" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 0DA2DA9A; Fri, 17 May 2024 13:19:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1715944785; bh=bVBSHHTwjk7r5Ay2aMI6ZrBecR5S06CsKavj2yj6LG0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Corjv+R+2zZ6IJvjwnyiMNKnavpJEKaA1rondWAfOpRYGBbOfJzI2jUG3W6q7SXjM 6csSmc+yFGE6mEG7hDh2Td3j6tVLcbWB9i2DIzNqEBrArjwT0cdHAx0u1iLa4TBxz1 xO9JRm/G7/8X0meZoODHd9csWHlMc8/PYpNkRzXA= Date: Fri, 17 May 2024 14:19:44 +0300 From: Laurent Pinchart To: Sakari Ailus Cc: ChiYuan Huang , Mauro Carvalho Chehab , Daniel Scally , Jean-Michel Hautbois , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] media: v4l: async: Fix NULL pointer when v4l2 flash subdev binding Message-ID: <20240517111944.GD19755@pendragon.ideasonboard.com> References: <20240517063150.GA12245@linuxcarl2.richtek.com> 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=utf-8 Content-Disposition: inline In-Reply-To: On Fri, May 17, 2024 at 08:00:32AM +0000, Sakari Ailus wrote: > Hi Chi Yuan, > > On Fri, May 17, 2024 at 02:31:50PM +0800, ChiYuan Huang wrote: > > 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'. > > Ah, right. I took a new look into the code and agree this is a problem. > This probably hasn't been hit previously as the root notifier driver tends > not to have any lens or flash devices. > > I'd change the commit message slightly: > > --------8<------------- > In v4l2_async_create_ancillary_links(), ancillary links are created for > lens and flash sub-devices. These are sub-device to sub-device links and if > the async notifier is related to a V4L2 device, the source sub-device of > the ancillary link is NULL, leading to a NULL pointer dereference. Check > the notifier's sd field is non-NULL in v4l2_async_create_ancillary_links(). > --------8<------------- What's the use case for including lens or flash devices in the root notifier ? Shouldn't lens and flash subdevices always be linked to something ? We should of course not crash, but it seems that simply ignoring the subdevs and not linking them isn't a great idea either. > > Or is it caused by the wrong usage? > > > > > > + > > > > link = media_create_ancillary_link(&n->sd->entity, &sd->entity); > > > > > > > > #endif -- Regards, Laurent Pinchart