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 0D904C433EF for ; Mon, 13 Jun 2022 12:16:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238585AbiFMMQI (ORCPT ); Mon, 13 Jun 2022 08:16:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1359054AbiFMMOi (ORCPT ); Mon, 13 Jun 2022 08:14:38 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A67D54F87; Mon, 13 Jun 2022 04:02:14 -0700 (PDT) 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 9734AB80E93; Mon, 13 Jun 2022 11:02:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0ACBC34114; Mon, 13 Jun 2022 11:02:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655118131; bh=4xrCwR+dSMUMl6tf6Scxfy8ADhapePz4RrscHl0msvY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Sc3ZJIzV+ES29zraMJSAph1pjC9f7QgqEIPgCGLpCklBtdd4LLrdiqzplQppbmyXi WZAR2HMo4CdGPFk3DfRwPomZCQoyukZisHREwYD0baAty9dgpK6JVvb6g2jlFdanQi sT/Esrt3WzcGH2YRsbhs0vTBJ8s6zSrNVo8xczxA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Duoming Zhou , Sasha Levin Subject: [PATCH 4.19 255/287] drivers: tty: serial: Fix deadlock in sa1100_set_termios() Date: Mon, 13 Jun 2022 12:11:19 +0200 Message-Id: <20220613094931.744548529@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094923.832156175@linuxfoundation.org> References: <20220613094923.832156175@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Duoming Zhou [ Upstream commit 62b2caef400c1738b6d22f636c628d9f85cd4c4c ] There is a deadlock in sa1100_set_termios(), which is shown below: (Thread 1) | (Thread 2) | sa1100_enable_ms() sa1100_set_termios() | mod_timer() spin_lock_irqsave() //(1) | (wait a time) ... | sa1100_timeout() del_timer_sync() | spin_lock_irqsave() //(2) (wait timer to stop) | ... We hold sport->port.lock in position (1) of thread 1 and use del_timer_sync() to wait timer to stop, but timer handler also need sport->port.lock in position (2) of thread 2. As a result, sa1100_set_termios() will block forever. This patch moves del_timer_sync() before spin_lock_irqsave() in order to prevent the deadlock. Signed-off-by: Duoming Zhou Link: https://lore.kernel.org/r/20220417111626.7802-1-duoming@zju.edu.cn Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/sa1100.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/sa1100.c b/drivers/tty/serial/sa1100.c index a399772be3fc..8a65fb1ce568 100644 --- a/drivers/tty/serial/sa1100.c +++ b/drivers/tty/serial/sa1100.c @@ -439,6 +439,8 @@ sa1100_set_termios(struct uart_port *port, struct ktermios *termios, baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16); quot = uart_get_divisor(port, baud); + del_timer_sync(&sport->timer); + spin_lock_irqsave(&sport->port.lock, flags); sport->port.read_status_mask &= UTSR0_TO_SM(UTSR0_TFS); @@ -469,8 +471,6 @@ sa1100_set_termios(struct uart_port *port, struct ktermios *termios, UTSR1_TO_SM(UTSR1_ROR); } - del_timer_sync(&sport->timer); - /* * Update the per-port timeout. */ -- 2.35.1