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 11202CCA481 for ; Tue, 7 Jun 2022 19:53:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357547AbiFGTub (ORCPT ); Tue, 7 Jun 2022 15:50:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354527AbiFGSrG (ORCPT ); Tue, 7 Jun 2022 14:47:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EFDC9B184; Tue, 7 Jun 2022 11:01:51 -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 dfw.source.kernel.org (Postfix) with ESMTPS id CFD4C617B0; Tue, 7 Jun 2022 18:01:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68AA9C34119; Tue, 7 Jun 2022 18:01:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1654624910; bh=4xrCwR+dSMUMl6tf6Scxfy8ADhapePz4RrscHl0msvY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=icE/E+//1clvF6H3osUzarQHJjqqNZlmjZfMTUjMkglGCsMm2CjD0dfK2d1cmBCZ2 NEEZ+rffVkfN1pxkI5gua7kYz+1tlozxev2N1ztKOB0GjOWwxp9OqYM4q9fN+u+b8a r2M+kSFf22qZdLWNni8rWB0kQ8a6dMOJ3pTSHwFPfZbRVi7TShk8seEymRp2awpwoz J2Tr7HQj28aniVoleiFe8aWbTdfXIuqGFR7VcUBwHbHGhKcKA1a5/8Nfw2nfp6/ZmI aTuuzHwhVw4aq0izws4hcn2uoKMDYn30tMYETmMl2bWdwg7XZ6R9xYEMrdAZRQ9YYs megXsVzVz8l/Q== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Duoming Zhou , Greg Kroah-Hartman , Sasha Levin , jirislaby@kernel.org, linux-serial@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 08/27] drivers: tty: serial: Fix deadlock in sa1100_set_termios() Date: Tue, 7 Jun 2022 14:01:12 -0400 Message-Id: <20220607180133.481701-8-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220607180133.481701-1-sashal@kernel.org> References: <20220607180133.481701-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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