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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 D75BCC433DF for ; Thu, 20 Aug 2020 10:16:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 97FE820855 for ; Thu, 20 Aug 2020 10:16:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597918591; bh=X1suX7Qlv6NKaP0F+j8HOT7oOO7Sv6ibjF/TiNE22J8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lkXz0XLVdPYu5Ii5hhIyOxVK+lyTqyF9+iBje8nB5icqPtOA8SJABcHXR1OjnSVCO +o8OAUtZ/Fnw2a52QxLbUthcZwPb6lHsegRgtj/hBeIx7q3ToBiMQH6CYW4E7/pkE9 v/0EagC3jdRTV633RD9JeNdXjL5i9m23f3/WjPJ0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730967AbgHTKQ3 (ORCPT ); Thu, 20 Aug 2020 06:16:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:35374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728691AbgHTKPq (ORCPT ); Thu, 20 Aug 2020 06:15:46 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B74752078D; Thu, 20 Aug 2020 10:15:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597918545; bh=X1suX7Qlv6NKaP0F+j8HOT7oOO7Sv6ibjF/TiNE22J8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vYaaoYQCF0M8WVzHXYvqgAko+JGcRlRFx0sj8gGaDo2VcJMMf8MIVOPomyBvifaf3 UTE3TWGgwun2oyxpo9bLWb3xh24cQy/fwgLwgjrZSP647ZKuxHMCu8KBYjKETLHIjw w6qB1LYZzx5T0YDhaFCObl/8nb+7Z/d4HpUZlG24= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Wolfram Sang , =?UTF-8?q?Niklas=20S=C3=B6derlund?= , Wolfram Sang , Sasha Levin Subject: [PATCH 4.14 208/228] i2c: rcar: avoid race when unregistering slave Date: Thu, 20 Aug 2020 11:23:03 +0200 Message-Id: <20200820091617.926678603@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820091607.532711107@linuxfoundation.org> References: <20200820091607.532711107@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wolfram Sang [ Upstream commit c7c9e914f9a0478fba4dc6f227cfd69cf84a4063 ] Due to the lockless design of the driver, it is theoretically possible to access a NULL pointer, if a slave interrupt was running while we were unregistering the slave. To make this rock solid, disable the interrupt for a short time while we are clearing the interrupt_enable register. This patch is purely based on code inspection. The OOPS is super-hard to trigger because clearing SAR (the address) makes interrupts even more unlikely to happen as well. While here, reinit SCR to SDBS because this bit should always be set according to documentation. There is no effect, though, because the interface is disabled. Fixes: 7b814d852af6 ("i2c: rcar: avoid race when unregistering slave client") Signed-off-by: Wolfram Sang Reviewed-by: Niklas Söderlund Signed-off-by: Wolfram Sang Signed-off-by: Sasha Levin --- drivers/i2c/busses/i2c-rcar.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 07305304712e1..ed0f068109785 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -815,12 +815,14 @@ static int rcar_unreg_slave(struct i2c_client *slave) WARN_ON(!priv->slave); - /* disable irqs and ensure none is running before clearing ptr */ + /* ensure no irq is running before clearing ptr */ + disable_irq(priv->irq); rcar_i2c_write(priv, ICSIER, 0); - rcar_i2c_write(priv, ICSCR, 0); + rcar_i2c_write(priv, ICSSR, 0); + enable_irq(priv->irq); + rcar_i2c_write(priv, ICSCR, SDBS); rcar_i2c_write(priv, ICSAR, 0); /* Gen2: must be 0 if not using slave */ - synchronize_irq(priv->irq); priv->slave = NULL; pm_runtime_put(rcar_i2c_priv_to_dev(priv)); -- 2.25.1