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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B85D8C433EF for ; Mon, 13 Dec 2021 14:50:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239741AbhLMOua (ORCPT ); Mon, 13 Dec 2021 09:50:30 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:54416 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239739AbhLMOuZ (ORCPT ); Mon, 13 Dec 2021 09:50:25 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8F9196112D; Mon, 13 Dec 2021 14:50:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F4048C3460D; Mon, 13 Dec 2021 14:50:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1639407022; bh=3RIGLsrBTZq02SmBvywAtNI7mOiPPJHAQxradN0nZTA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=JNMisQxiaMBQv9WAMyx5F9doufgHMtM6+NCPoKl2BGNkcUwLSywlxGsmayTXh1ATk zfUt3PcQgGpv7+GloPaCbRKSNvZY87zgCzdfNJuQ84uB9Y2vkJaPu4O5Fpl+Rq7NEE Pdj5N18wT7fZenAVnl2OT4Sw4EOwkc6aG+AHw/UgAwLdpEfjsK8jSq1oDXBseWX4My yw6PYEwzjjtC6A6ulci4D5zGFpPq9hHaRl7Pb6bfdAZeXpuOyv+U8ED4nIVWQk51LV kCthSMQtcVh8A/5Ti/8QNYTOXh2H7A+mNAkPWy12sI/EhXvGFVb1LK/kV09Esrb4+4 MYojcPvaY9EZw== Received: by mail-ed1-f50.google.com with SMTP id l25so53297684eda.11; Mon, 13 Dec 2021 06:50:21 -0800 (PST) X-Gm-Message-State: AOAM532cRL7dXo68S9pfh3OEhZ/jlfoKnWk19HyHEWoqETER3l0t/TTx n6ZN+7Ze50giyjOYH5ftV3LA+e61ZPbvrEzfOA== X-Google-Smtp-Source: ABdhPJyZy7fUpjvl/N9Q0Pd+kRFxXN8zC9h0kK8pSs17SFmHjmePfgukBJCcEPO2aRlYuio3nyzSRB5ikVQH8Eng0z4= X-Received: by 2002:a17:907:72c2:: with SMTP id du2mr44725131ejc.155.1639407019675; Mon, 13 Dec 2021 06:50:19 -0800 (PST) MIME-Version: 1.0 References: <20211212062407.138309-1-marcan@marcan.st> <20211212062407.138309-2-marcan@marcan.st> <63334964-d63d-7625-e46f-a6e6ec19e908@marcan.st> In-Reply-To: From: Rob Herring Date: Mon, 13 Dec 2021 08:50:07 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 1/3] of: Move simple-framebuffer device handling from simplefb to of To: Javier Martinez Canillas Cc: Hector Martin , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Hans de Goede , Alyssa Rosenzweig , Pekka Paalanen , devicetree@vger.kernel.org, dri-devel , Linux Kernel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 13, 2021 at 5:30 AM Javier Martinez Canillas wrote: > > On Mon, Dec 13, 2021 at 11:46 AM Hector Martin wrote: > > > > On 13/12/2021 17.44, Javier Martinez Canillas wrote: > > > Hello Hector, > > > > > > On Sun, Dec 12, 2021 at 7:24 AM Hector Martin wrote: > > >> > > >> This code is required for both simplefb and simpledrm, so let's move it > > >> into the OF core instead of having it as an ad-hoc initcall in the > > >> drivers. > > >> > > >> Acked-by: Thomas Zimmermann > > >> Signed-off-by: Hector Martin > > >> --- > > >> drivers/of/platform.c | 4 ++++ > > >> drivers/video/fbdev/simplefb.c | 21 +-------------------- > > >> 2 files changed, 5 insertions(+), 20 deletions(-) > > >> > > > > > > This is indeed a much better approach than what I suggested. I just > > > have one comment. > > > > > >> diff --git a/drivers/of/platform.c b/drivers/of/platform.c > > >> index b3faf89744aa..793350028906 100644 > > >> --- a/drivers/of/platform.c > > >> +++ b/drivers/of/platform.c > > >> @@ -540,6 +540,10 @@ static int __init of_platform_default_populate_init(void) > > >> of_node_put(node); > > >> } > > >> > > >> + node = of_get_compatible_child(of_chosen, "simple-framebuffer"); > > > > > > You have to check if the node variable is NULL here. > > > > > >> + of_platform_device_create(node, NULL, NULL); > > > > > > Otherwise this could lead to a NULL pointer dereference if debug > > > output is enabled (the node->full_name is printed). > > > > Where is it printed? I thought I might need a NULL check, but this code > > Sorry, I misread of_amba_device_create() as > of_platform_device_create(), which uses the "%pOF" printk format > specifier [0] to print the node's full name as a debug output [1]. > > [0]: https://elixir.bootlin.com/linux/v5.16-rc5/source/Documentation/core-api/printk-formats.rst#L462 > [1]: https://elixir.bootlin.com/linux/v5.16-rc5/source/drivers/of/platform.c#L233 > > > was suggested verbatim by Rob in v2 without the NULL check and digging > > through I found that the NULL codepath is safe. > > > > You are right that passing NULL is a safe code path for now due the > of_device_is_available(node) check, but that seems fragile to me since > just adding a similar debug output to of_platform_device_create() > could trigger the NULL pointer dereference. All/most DT functions work with a NULL node ptr, so why should this one be different? Rob