Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753502AbdHROAK (ORCPT ); Fri, 18 Aug 2017 10:00:10 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:55261 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752623AbdHRNPm (ORCPT ); Fri, 18 Aug 2017 09:15:42 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Ajay Kaher" , "Alan Stern" , "Greg Kroah-Hartman" Date: Fri, 18 Aug 2017 14:13:20 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 018/134] USB: Proper handling of Race Condition when two USB class drivers try to call init_usb_class simultaneously In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1779 Lines: 59 3.16.47-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Ajay Kaher commit 2f86a96be0ccb1302b7eee7855dbee5ce4dc5dfb upstream. There is race condition when two USB class drivers try to call init_usb_class at the same time and leads to crash. code path: probe->usb_register_dev->init_usb_class To solve this, mutex locking has been added in init_usb_class() and destroy_usb_class(). As pointed by Alan, removed "if (usb_class)" test from destroy_usb_class() because usb_class can never be NULL there. Signed-off-by: Ajay Kaher Acked-by: Alan Stern Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/usb/core/file.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/drivers/usb/core/file.c +++ b/drivers/usb/core/file.c @@ -26,6 +26,7 @@ #define MAX_USB_MINORS 256 static const struct file_operations *usb_minors[MAX_USB_MINORS]; static DECLARE_RWSEM(minor_rwsem); +static DEFINE_MUTEX(init_usb_class_mutex); static int usb_open(struct inode *inode, struct file *file) { @@ -108,8 +109,9 @@ static void release_usb_class(struct kre static void destroy_usb_class(void) { - if (usb_class) - kref_put(&usb_class->kref, release_usb_class); + mutex_lock(&init_usb_class_mutex); + kref_put(&usb_class->kref, release_usb_class); + mutex_unlock(&init_usb_class_mutex); } int usb_major_init(void) @@ -171,7 +173,10 @@ int usb_register_dev(struct usb_interfac if (intf->minor >= 0) return -EADDRINUSE; + mutex_lock(&init_usb_class_mutex); retval = init_usb_class(); + mutex_unlock(&init_usb_class_mutex); + if (retval) return retval;