From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.19]) (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 680D922318; Fri, 17 May 2024 08:00:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.19 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715932839; cv=none; b=fGCN4zoWBkBwUf8eOdh8W4HPQx+DZXAxXXDLtJF7LRFdjiEPgw564hRwLzHu9+f0FfQIk/szUIeJo3LWM4L6UYo4qij+X9ZAbfZmwesaatGu3dylVpN0s08zwKAsM+hRJ8huB7a+NKgFaZH6mAh3hW8CdZoixG+RgMUOJtvKRQk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715932839; c=relaxed/simple; bh=QxgA8GZnoup8zGH9AmZ4cladIL6JafKC2tee8EIHg/o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i2kLWD9hhOMT3BflT2LL0i7B5+4VR8230BV429is5oIaFT9262p4MfJSmFjOFZOCRjw0B2697OqEm0pKlGzZm1ck3lKsev2ROZoseL41ujzXuDzsDoKcD8qnaJtBwrD22FMgJ3ClwLRfTmE8hHaW3IY/AAr7BIGMxvEwQqmXUtA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=djaxws3o; arc=none smtp.client-ip=192.198.163.19 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="djaxws3o" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1715932838; x=1747468838; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=QxgA8GZnoup8zGH9AmZ4cladIL6JafKC2tee8EIHg/o=; b=djaxws3oJzRB4mp9eq2cYEWXO3wu+1dlnJkR+DTPCkg6I2W1dIIHBBqC B4QC/lhWQJpDP9ctTqZH1So3aZKvwE3PP7b3lOrnmTnQ0E1u96qSBEtZp lXnaoRf2nzZzm/DRiawKLXjOMgF08S6M73v/ctP38+4yDQeu7aI+hbu33 Gelvh8p4ux3Zz5slSUvtVZaA18hB/DcQKXW+QmVTXKJGCGf9Fpcc911PZ rN62dYnNHK8HEpOCMGgFZeigLZyO/47Wk9dp7EmZNxfoNCpadhtyi8vb4 i0KxlrdGWKWQ9x5X+qk1VB7VlT5dAKSdXitbjsu3HNZnf0B+GPLyjz4YN Q==; X-CSE-ConnectionGUID: hMHaV31sSyWuAcfDFjxfTQ== X-CSE-MsgGUID: Q0tWMaZLRtC3fkK25ZhO5A== X-IronPort-AV: E=McAfee;i="6600,9927,11074"; a="11936373" X-IronPort-AV: E=Sophos;i="6.08,167,1712646000"; d="scan'208";a="11936373" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 May 2024 01:00:37 -0700 X-CSE-ConnectionGUID: a9vvjHZlRoqS19wgv+zALQ== X-CSE-MsgGUID: Hetpc9OuS2iqE3maXU0NqQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,167,1712646000"; d="scan'208";a="62918843" Received: from turnipsi.fi.intel.com (HELO kekkonen.fi.intel.com) ([10.237.72.44]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 May 2024 01:00:35 -0700 Received: from kekkonen.localdomain (localhost [127.0.0.1]) by kekkonen.fi.intel.com (Postfix) with SMTP id 34A9B11FA44; Fri, 17 May 2024 11:00:32 +0300 (EEST) Date: Fri, 17 May 2024 08:00:32 +0000 From: Sakari Ailus To: ChiYuan Huang Cc: Mauro Carvalho Chehab , Daniel Scally , Laurent Pinchart , 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: References: <20240517063150.GA12245@linuxcarl2.richtek.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240517063150.GA12245@linuxcarl2.richtek.com> 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<------------- > > Or is it caused by the wrong usage? > > > > + > > > link = media_create_ancillary_link(&n->sd->entity, &sd->entity); > > > > > > #endif > > -- Kind regards, Sakari Ailus