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 20AE8C4321E for ; Fri, 2 Dec 2022 15:45:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233775AbiLBPpa (ORCPT ); Fri, 2 Dec 2022 10:45:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49150 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233675AbiLBPp1 (ORCPT ); Fri, 2 Dec 2022 10:45:27 -0500 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96E15D5876; Fri, 2 Dec 2022 07:45:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1669995926; x=1701531926; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=GcRX7WmZAbCTPDq8gE+aA0ZUaodFBclsrxsx/rt7bwU=; b=Tl7GV7kOIgEtV57qw381xD9na7npvREq5W5hgaT3fKT88LXa3cB9C1AQ 7VawILLZyGU6D4gov7fdEa9yD8KsmrNIFT+LzsFvUOktexTZvKJgUOA6U iHb8oakWllAvmlqqNaP6DmOnTYwgN4vxV4uUvXYvWjgInBCUWE6D2p/Rx ZTkGiHigwP/8pLoNS3nuOUjCPiLvctBEABXtplq6rbpzsd5f49wmL54MY K3JjB7RyvNb3uJ3WTTlY/xBiII5RLQjDHpm1PPY45U4NXMcKZnlWDw/Ly tJS2GRxKoDLgOWLvCVZmHNiJirE0CxgcWMZ8Yd5i+u1X3YeGQ+NfMz14b A==; X-IronPort-AV: E=McAfee;i="6500,9779,10548"; a="314679304" X-IronPort-AV: E=Sophos;i="5.96,212,1665471600"; d="scan'208";a="314679304" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Dec 2022 07:45:03 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10548"; a="751306221" X-IronPort-AV: E=Sophos;i="5.96,212,1665471600"; d="scan'208";a="751306221" Received: from smile.fi.intel.com ([10.237.72.54]) by fmsmga002.fm.intel.com with ESMTP; 02 Dec 2022 07:45:01 -0800 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1p18Dj-003XZC-0E; Fri, 02 Dec 2022 17:44:59 +0200 Date: Fri, 2 Dec 2022 17:44:58 +0200 From: Andy Shevchenko To: Bartosz Golaszewski Cc: Kent Gibson , Linus Walleij , Nick Hainke , linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: Re: [PATCH v7 2/2] gpiolib: protect the GPIO device against being dropped while in use by user-space Message-ID: References: <20221202150444.244313-1-brgl@bgdev.pl> <20221202150444.244313-3-brgl@bgdev.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221202150444.244313-3-brgl@bgdev.pl> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 02, 2022 at 04:04:44PM +0100, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski > > While any of the GPIO cdev syscalls is in progress, the kernel can call > gpiochip_remove() (for instance, when a USB GPIO expander is disconnected) > which will set gdev->chip to NULL after which any subsequent access will > cause a crash. > > To avoid that: use an RW-semaphore in which the syscalls take it for > reading (so that we don't needlessly prohibit the user-space from calling > syscalls simultaneously) while gpiochip_remove() takes it for writing so > that it can only happen once all syscalls return. > > Fixes: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines") > Fixes: 3c0d9c635ae2 ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL") > Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL") > Fixes: a54756cb24ea ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL") > Fixes: 7b8e00d98168 ("gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL") > Signed-off-by: Bartosz Golaszewski > [Nick: fixed a build failure with CDEV_V1 disabled] > Co-authored-by: Nick Hainke In Linux kernel there is no such tag. And in case you want to use Co-developed-by, you also need to add the respective SoB one. > Reviewed-by: Kent Gibson > Reviewed-by: Andy Shevchenko > Reviewed-by: Linus Walleij -- With Best Regards, Andy Shevchenko