Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936803AbdCJMPo (ORCPT ); Fri, 10 Mar 2017 07:15:44 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45142 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936790AbdCJMPm (ORCPT ); Fri, 10 Mar 2017 07:15:42 -0500 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, "Greg Kroah-Hartman" , "Mathias Nyman" , "Baolin Wang" Date: Fri, 10 Mar 2017 11:46:22 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 152/370] xhci: Handle command completion and timeout race 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: 1768 Lines: 47 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Mathias Nyman commit a5a1b9514154437aa1ed35c291191f82fd3e941a upstream. If we get a command completion event at the same time as the command timeout work starts on another cpu we might end up aborting the wrong command. If the command completion takes the xhci lock before the timeout work, it will handle the command, pick the next command, mark it as current_cmd, and re-queue the timeout work. When the timeout work finally gets the lock It will start aborting the wrong command. This case can be resolved by checking if the timeout work is pending inside the timeout function itself. A new timeout work can only be pending if the command completed and a new command was queued. If there are no more commands pending then command completion will set the current_cmd to NULL, which is already handled in the timeout work. Reported-by: Baolin Wang Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/usb/host/xhci-ring.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1294,7 +1294,11 @@ void xhci_handle_command_timeout(unsigne spin_lock_irqsave(&xhci->lock, flags); - if (!xhci->current_cmd) { + /* + * If timeout work is pending, or current_cmd is NULL, it means we + * raced with command completion. Command is handled so just return. + */ + if (!xhci->current_cmd || timer_pending(&xhci->cmd_timer)) { spin_unlock_irqrestore(&xhci->lock, flags); return; }