From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937569AbdAJNih (ORCPT ); Tue, 10 Jan 2017 08:38:37 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:59538 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937409AbdAJNie (ORCPT ); Tue, 10 Jan 2017 08:38:34 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lu Baolu , Mathias Nyman Subject: [PATCH 4.4 019/101] usb: xhci: fix possible wild pointer Date: Tue, 10 Jan 2017 14:36:32 +0100 Message-Id: <20170110131523.357692868@linuxfoundation.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170110131522.493717794@linuxfoundation.org> References: <20170110131522.493717794@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lu Baolu commit 2b985467371a58ae44d76c7ba12b0951fee6ed98 upstream. handle_cmd_completion() frees a command structure which might be still referenced by xhci->current_cmd. This might cause problem when xhci->current_cmd is accessed after that. A real-life case could be like this. The host takes a very long time to respond to a command, and the command timer is fired at the same time when the command completion event arrives. The command completion handler frees xhci->current_cmd before the timer function can grab xhci->lock. Afterward, timer function grabs the lock and go ahead with checking and setting members of xhci->current_cmd. Signed-off-by: Lu Baolu Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-ring.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1268,14 +1268,18 @@ void xhci_handle_command_timeout(unsigne bool second_timeout = false; xhci = (struct xhci_hcd *) data; - /* mark this command to be cancelled */ spin_lock_irqsave(&xhci->lock, flags); - if (xhci->current_cmd) { - if (xhci->current_cmd->status == COMP_CMD_ABORT) - second_timeout = true; - xhci->current_cmd->status = COMP_CMD_ABORT; + + if (!xhci->current_cmd) { + spin_unlock_irqrestore(&xhci->lock, flags); + return; } + /* mark this command to be cancelled */ + if (xhci->current_cmd->status == COMP_CMD_ABORT) + second_timeout = true; + xhci->current_cmd->status = COMP_CMD_ABORT; + /* Make sure command ring is running before aborting it */ hw_ring_state = xhci_read_64(xhci, &xhci->op_regs->cmd_ring); if ((xhci->cmd_ring_state & CMD_RING_STATE_RUNNING) && @@ -1424,6 +1428,8 @@ static void handle_cmd_completion(struct xhci->current_cmd = list_entry(cmd->cmd_list.next, struct xhci_command, cmd_list); mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT); + } else if (xhci->current_cmd == cmd) { + xhci->current_cmd = NULL; } event_handled: