From patchwork Mon Feb 28 17:24:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 547084 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 6AFF3C433FE for ; Mon, 28 Feb 2022 17:54:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234340AbiB1RzC (ORCPT ); Mon, 28 Feb 2022 12:55:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239611AbiB1RxO (ORCPT ); Mon, 28 Feb 2022 12:53:14 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8ED6DAA012; Mon, 28 Feb 2022 09:40:39 -0800 (PST) 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 ams.source.kernel.org (Postfix) with ESMTPS id 411BBB815BA; Mon, 28 Feb 2022 17:40:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8CC9DC340E7; Mon, 28 Feb 2022 17:40:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646070036; bh=5uF6y4pkw02E5d5b+6ZDIAcWCGP3fx5/Fm1OO0TLlEc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LITZ/A7vTYp45O5NF4E5SixxUsumwBvJ6/4DmyDWpxspTrDq+/D7kbYNfzmAx2i6n zUPO+kKBzUcNUQInDuCfNJ1e0MQ71U2MvRjpwESlCP5SruYFb6NzfsG0AhYQE1YHxd 1XNO35fRfDyHW+rpXyImPR9tERj/q50+A+Ul5c0I= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Phil Elwell Subject: [PATCH 5.15 103/139] sc16is7xx: Fix for incorrect data being transmitted Date: Mon, 28 Feb 2022 18:24:37 +0100 Message-Id: <20220228172358.504935085@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220228172347.614588246@linuxfoundation.org> References: <20220228172347.614588246@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Phil Elwell commit eebb0f4e894f1e9577a56b337693d1051dd6ebfd upstream. UART drivers are meant to use the port spinlock within certain methods, to protect against reentrancy. The sc16is7xx driver does very little locking, presumably because when added it triggers "scheduling while atomic" errors. This is due to the use of mutexes within the regmap abstraction layer, and the mutex implementation's habit of sleeping the current thread while waiting for access. Unfortunately this lack of interlocking can lead to corruption of outbound data, which occurs when the buffer used for I2C transmission is used simultaneously by two threads - a work queue thread running sc16is7xx_tx_proc, and an IRQ thread in sc16is7xx_port_irq, both of which can call sc16is7xx_handle_tx. An earlier patch added efr_lock, a mutex that controls access to the EFR register. This mutex is already claimed in the IRQ handler, and all that is required is to claim the same mutex in sc16is7xx_tx_proc. See: https://github.com/raspberrypi/linux/issues/4885 Fixes: 6393ff1c4435 ("sc16is7xx: Use threaded IRQ") Cc: stable Signed-off-by: Phil Elwell Link: https://lore.kernel.org/r/20220216160802.1026013-1-phil@raspberrypi.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/sc16is7xx.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -734,12 +734,15 @@ static irqreturn_t sc16is7xx_irq(int irq static void sc16is7xx_tx_proc(struct kthread_work *ws) { struct uart_port *port = &(to_sc16is7xx_one(ws, tx_work)->port); + struct sc16is7xx_port *s = dev_get_drvdata(port->dev); if ((port->rs485.flags & SER_RS485_ENABLED) && (port->rs485.delay_rts_before_send > 0)) msleep(port->rs485.delay_rts_before_send); + mutex_lock(&s->efr_lock); sc16is7xx_handle_tx(port); + mutex_unlock(&s->efr_lock); } static void sc16is7xx_reconf_rs485(struct uart_port *port)