From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EBBD1C2BA2B for ; Fri, 10 Apr 2020 11:15:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96FBA20753 for ; Fri, 10 Apr 2020 11:15:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="RsMl3mmE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726007AbgDJLPf (ORCPT ); Fri, 10 Apr 2020 07:15:35 -0400 Received: from perceval.ideasonboard.com ([213.167.242.64]:40286 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726595AbgDJLPb (ORCPT ); Fri, 10 Apr 2020 07:15:31 -0400 Received: from pendragon.ideasonboard.com (81-175-216-236.bb.dnainternet.fi [81.175.216.236]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id D17A5329; Fri, 10 Apr 2020 13:15:29 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1586517330; bh=EC1Za9eW5ayrdbiizZc2mUGuvzN/kcydyN/KK+vY6fo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RsMl3mmEriIW3Xg7tCFjYtChXNDacoM3uCrHvj8hHbnj7faR1UY/L7pt8w0t5kVsQ 9sND9qwlvvfYe+xJl7UqBGH6OT6FCiAqqZI8mYmTVCW7j9rUPTx4VHgNugGBlu1zoA hKObqcQSI8XpvwhFBUXHRo7BygaWARNs0KBkZjPg= Date: Fri, 10 Apr 2020 14:15:19 +0300 From: Laurent Pinchart To: Kieran Bingham Cc: Sakari Ailus , linux-renesas-soc@vger.kernel.org, Jacopo Mondi , Niklas =?utf-8?Q?S=C3=B6derlund?= , Hyun Kwon , Manivannan Sadhasivam Subject: Re: [PATCH v8 02/13] squash! max9286: convert probe kzalloc Message-ID: <20200410111519.GA4751@pendragon.ideasonboard.com> References: <20200409121202.11130-1-kieran.bingham+renesas@ideasonboard.com> <20200409121202.11130-3-kieran.bingham+renesas@ideasonboard.com> <20200409163333.GA25086@pendragon.ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: linux-renesas-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org Hi Kieran, On Fri, Apr 10, 2020 at 09:20:25AM +0100, Kieran Bingham wrote: > On 09/04/2020 17:33, Laurent Pinchart wrote: > > On Thu, Apr 09, 2020 at 01:11:51PM +0100, Kieran Bingham wrote: > >> v8: > >> - Convert probe kzalloc usage to devm_ variant > > > > This isn't worse than the existing code, but are you aware that devm_* > > should not be used in this case ? The memory should be allocated with > > kzalloc() and freed in the .release() operation. > > This change was at the request of a review comment from Sakari. > > From: > https://lore.kernel.org/linux-media/4139f241-2fde-26ad-fe55-dcaeb76ad6cc@ideasonboard.com/ > > >>> + > >>> +static int max9286_probe(struct i2c_client *client) > >>> +{ > >>> + struct max9286_priv *priv; > >>> + unsigned int i; > >>> + int ret; > >>> + > >>> + priv = kzalloc(sizeof(*priv), GFP_KERNEL); > >>> + if (!priv) > >>> + return -ENOMEM; > >> > >> You won't lose anything by using the devm_ variant here. > > > > Indeed, > > > >>> + > >>> + priv->client = client; > >>> + i2c_set_clientdata(client, priv); > >>> + > >>> + for (i = 0; i < MAX9286_N_SINKS; i++) > >>> + max9286_init_format(&priv->fmt[i]); > >>> + > >>> + ret = max9286_parse_dt(priv); > >>> + if (ret) > >>> + return ret; > >> > >> But you can avoid accidental memory leaks for nothing. :-) > > > > It would be good not to leak indeed! > > I understand that there are lifetime issues in V4L2 - but in my opinion > that needs to be handled by core V4l2 (and or support from driver core > framework). I'm afraid that's not possible. The V4L2 core can't delay remove(). There are helpers we could create to simplify correct memory management for drivers, but in any case, devm_kzalloc() isn't correct. There are also issues in the core that would make unbinding unsafe even if correctly implemented in this driver, but a correct implementation in drivers will be required in any case. As I said before this patch isn't a regression as memory allocation is already broken here, but it doesn't go in the right direction either. > Also - isn't it highly unlikely to affect the max9286? Isn't the > lifetime issue that the device can be unplugged while the file handle is > open? > > I don't think anyone is going to 'unplug' the max9286 while it's active :-) No, but someone could unbind it through sysfs. In any case it's not an excuse to not implement memory allocation correctly :-) > >> --- > >> drivers/media/i2c/max9286.c | 5 +---- > >> 1 file changed, 1 insertion(+), 4 deletions(-) > >> > >> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c > >> index b84d2daa6561..0a43137b8112 100644 > >> --- a/drivers/media/i2c/max9286.c > >> +++ b/drivers/media/i2c/max9286.c > >> @@ -1155,7 +1155,7 @@ static int max9286_probe(struct i2c_client *client) > >> unsigned int i; > >> int ret; > >> > >> - priv = kzalloc(sizeof(*priv), GFP_KERNEL); > >> + priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL); > >> if (!priv) > >> return -ENOMEM; > >> > >> @@ -1232,7 +1232,6 @@ static int max9286_probe(struct i2c_client *client) > >> max9286_configure_i2c(priv, false); > >> err_free: > >> max9286_cleanup_dt(priv); > >> - kfree(priv); > >> > >> return ret; > >> } > >> @@ -1253,8 +1252,6 @@ static int max9286_remove(struct i2c_client *client) > >> > >> gpiod_set_value_cansleep(priv->gpiod_pwdn, 0); > >> > >> - kfree(priv); > >> - > >> return 0; > >> } > >> -- Regards, Laurent Pinchart