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 5BEA7EB64DA for ; Tue, 18 Jul 2023 14:42:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233295AbjGROmN (ORCPT ); Tue, 18 Jul 2023 10:42:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230221AbjGROmL (ORCPT ); Tue, 18 Jul 2023 10:42:11 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FE9EEC; Tue, 18 Jul 2023 07:42:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1689691329; x=1721227329; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=WozK0FLM9qmME1gbk1x85asqParkBU93wFxvIidHN9A=; b=bc860qFMg2B0KCy6SsJjargd6KIhyVs9+d+v9hw/fNzSDlKHJZFIt3hb cGpmGQzXMVhzDHXwF4t1Kq4KCXw0z6knRXVDddj9OZw1NcVf1+yL6CywJ bG3J70UYsOyNjY1RGheumRicExrqHtI+wJHFZ/kP+JbFu/dBXeiOjncX7 r2XS78gueyX9UzG7yaC+kzGzowcRAjv6c1c83WTnxp5XLL2j2raWMgrA0 2OV+6IBSZ+k59Lv8E41VFON/VpqedBkx7pcT5KMeR51SMzHnbpKGjDTwa D47L+tc9mdFl69xvbgyyW1zOzoJ5Wvl2FD18VTaJLIE+T02O/qlzSgd82 A==; X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="432405303" X-IronPort-AV: E=Sophos;i="6.01,214,1684825200"; d="scan'208";a="432405303" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2023 07:42:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="723653191" X-IronPort-AV: E=Sophos;i="6.01,214,1684825200"; d="scan'208";a="723653191" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga002.jf.intel.com with ESMTP; 18 Jul 2023 07:42:08 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1qLltu-0000UD-0X; Tue, 18 Jul 2023 17:42:06 +0300 Date: Tue, 18 Jul 2023 17:42:05 +0300 From: Andy Shevchenko To: Milan Zamazal Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Jonathan Cameron , Lars-Peter Clausen Subject: Re: [PATCH] iio: core: Prevent invalid memory access when there is no parent Message-ID: References: <20230718120700.132579-1-mzamazal@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230718120700.132579-1-mzamazal@redhat.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 18, 2023 at 02:07:00PM +0200, Milan Zamazal wrote: > Commit 813665564b3d ("iio: core: Convert to use firmware node handle > instead of OF node") switched the kind of nodes to use for label > retrieval in device registration. Probably an unwanted change in that > commit was that if the device has no parent then NULL pointer is > accessed. This is what happens in the stock IIO dummy driver when a > new entry is created in configfs: > # mkdir /sys/kernel/config/iio/devices/dummy/foo > BUG: kernel NULL pointer dereference, address: 0000000000000278 > ... > ? asm_exc_page_fault+0x22/0x30 > ? container_offline+0x20/0x20 > __iio_device_register+0x45/0xc10 > ? krealloc+0x73/0xa0 > ? iio_device_attach_buffer+0x31/0xc0 > ? iio_simple_dummy_configure_buffer+0x20/0x20 > ? iio_triggered_buffer_setup_ext+0xb4/0x100 > iio_dummy_probe+0x112/0x190 > iio_sw_device_create+0xa8/0xd0 > device_make_group+0xe/0x40 > configfs_mkdir+0x1a6/0x440 Read this https://www.kernel.org/doc/html/latest/process/submitting-patches.html#backtraces-in-commit-messages and amend the commit message accordingly. > Since there seems to be no reason to make a parent device of an IIO > dummy device mandatory, let’s prevent the invalid memory access in > __iio_device_register when the parent device is NULL. With this > change, the IIO dummy driver works fine with configfs. ... > int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod) > { > struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev); > - struct fwnode_handle *fwnode; > + struct fwnode_handle *fwnode = NULL; > int ret; > > if (!indio_dev->info) > /* If the calling driver did not initialize firmware node, do it here */ > if (dev_fwnode(&indio_dev->dev)) > fwnode = dev_fwnode(&indio_dev->dev); > - else > + else if (indio_dev->dev.parent != NULL) > fwnode = dev_fwnode(indio_dev->dev.parent); This part of the change is okay with dropped " != NULL". > - device_set_node(&indio_dev->dev, fwnode); > - > - fwnode_property_read_string(fwnode, "label", &indio_dev->label); > + if (fwnode != NULL) { > + device_set_node(&indio_dev->dev, fwnode); > + fwnode_property_read_string(fwnode, "label", &indio_dev->label); > + } This part of the change is not needed. -- With Best Regards, Andy Shevchenko