From patchwork Thu Apr 27 13:33:44 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Neukum X-Patchwork-Id: 13225491 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 8ECB2C77B73 for ; Thu, 27 Apr 2023 13:33:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243665AbjD0Nd6 (ORCPT ); Thu, 27 Apr 2023 09:33:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232894AbjD0Nd4 (ORCPT ); Thu, 27 Apr 2023 09:33:56 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8BC0C18C; Thu, 27 Apr 2023 06:33:55 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 4618921B3F; Thu, 27 Apr 2023 13:33:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1682602434; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wd+p9adp/HcJc7Th+S4UjCWxhF9jWQwIyXD1bb94NMQ=; b=AUJ1nVH4EOHXydXh/4AKbyc0BIWTEHLyZn9UrXn55dRnYE47NbYsflM0l2laC2wzXzsGUV sUhG5YzbfNBIo3CEx8HVgSw5Zqw1WFe+DArS7i+h5kaR/66D8dzUNtpSMur3RNjZ30l+3A 7cPnR9bOr8KUt6uidQN1noEaY1HDGwg= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 00092138F9; Thu, 27 Apr 2023 13:33:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id yF7wOMF5SmSVeQAAMHmgww (envelope-from ); Thu, 27 Apr 2023 13:33:53 +0000 From: Oliver Neukum To: wim@linux-watchdog.org, linux@roeck-us.net, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Oliver Neukum Subject: [PATCH 2/8] pcwd_usb: stop open race disconnect Date: Thu, 27 Apr 2023 15:33:44 +0200 Message-Id: <20230427133350.31064-3-oneukum@suse.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230427133350.31064-1-oneukum@suse.com> References: <20230427133350.31064-1-oneukum@suse.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org There is a mutex already taken in disconnect. And it even has the correct comment. It just has to be taken in open and disconnect, too, to prevent the race. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Oliver Neukum --- drivers/watchdog/pcwd_usb.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/watchdog/pcwd_usb.c b/drivers/watchdog/pcwd_usb.c index 3a22291d633b..d5d68a529620 100644 --- a/drivers/watchdog/pcwd_usb.c +++ b/drivers/watchdog/pcwd_usb.c @@ -476,14 +476,21 @@ static long usb_pcwd_ioctl(struct file *file, unsigned int cmd, static int usb_pcwd_open(struct inode *inode, struct file *file) { + int retval = -EBUSY; + + mutex_lock(&disconnect_mutex); /* /dev/watchdog can only be opened once */ if (test_and_set_bit(0, &is_active)) - return -EBUSY; + goto error; /* Activate */ usb_pcwd_start(usb_pcwd_device); usb_pcwd_keepalive(usb_pcwd_device); - return stream_open(inode, file); + retval = stream_open(inode, file); + +error: + mutex_unlock(&disconnect_mutex); + return retval; } static int usb_pcwd_release(struct inode *inode, struct file *file) @@ -522,7 +529,13 @@ static ssize_t usb_pcwd_temperature_read(struct file *file, char __user *data, static int usb_pcwd_temperature_open(struct inode *inode, struct file *file) { - return stream_open(inode, file); + int retval; + + mutex_lock(&disconnect_mutex); + retval = stream_open(inode, file); + mutex_unlock(&disconnect_mutex); + + return retval; } static int usb_pcwd_temperature_release(struct inode *inode, struct file *file)