patch "usb: xhci: hold lock over xhci_abort_cmd_ring()" added to usb-linus

patch "usb: xhci: hold lock over xhci_abort_cmd_ring()" added to usb-linus

[gregkh]

This is a note to let you know that I've just added the patch titled

    usb: xhci: hold lock over xhci_abort_cmd_ring()

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From 4dea70778c0f48b4385c7720c363ec8d37a401b4 Mon Sep 17 00:00:00 2001
From: Lu Baolu <baolu.lu@linux.intel.com>
Date: Tue, 3 Jan 2017 18:28:49 +0200
Subject: usb: xhci: hold lock over xhci_abort_cmd_ring()

In command timer function, xhci_handle_command_timeout(), xhci->lock
is unlocked before call into xhci_abort_cmd_ring(). This might cause
race between the timer function and the event handler.

The xhci_abort_cmd_ring() function sets the CMD_RING_ABORT bit in the
command register and polling it until the setting takes effect. A stop
command ring event might be handled between writing the abort bit and
polling for it. The event handler will restart the command ring, which
causes the failure of polling, and we ever believed that we failed to
stop it.

As a bonus, this also fixes some issues of calling functions without
locking in xhci_handle_command_timeout().

Cc: <stable@vger.kernel.org> # 3.7+
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/host/xhci-ring.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 935193c6bf23..2f453e442ac7 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1287,29 +1287,34 @@ void xhci_handle_command_timeout(unsigned long data)
 	hw_ring_state = xhci_read_64(xhci, &xhci->op_regs->cmd_ring);
 	if ((xhci->cmd_ring_state & CMD_RING_STATE_RUNNING) &&
 	    (hw_ring_state & CMD_RING_RUNNING))  {
-		spin_unlock_irqrestore(&xhci->lock, flags);
 		xhci_dbg(xhci, "Command timeout\n");
 		ret = xhci_abort_cmd_ring(xhci);
 		if (unlikely(ret == -ESHUTDOWN)) {
 			xhci_err(xhci, "Abort command ring failed\n");
 			xhci_cleanup_command_queue(xhci);
+			spin_unlock_irqrestore(&xhci->lock, flags);
 			usb_hc_died(xhci_to_hcd(xhci)->primary_hcd);
 			xhci_dbg(xhci, "xHCI host controller is dead.\n");
+
+			return;
 		}
-		return;
+
+		goto time_out_completed;
 	}
 
 	/* command ring failed to restart, or host removed. Bail out */
 	if (second_timeout || xhci->xhc_state & XHCI_STATE_REMOVING) {
-		spin_unlock_irqrestore(&xhci->lock, flags);
 		xhci_dbg(xhci, "command timed out twice, ring start fail?\n");
 		xhci_cleanup_command_queue(xhci);
-		return;
+
+		goto time_out_completed;
 	}
 
 	/* command timeout on stopped ring, ring can't be aborted */
 	xhci_dbg(xhci, "Command timeout on stopped ring\n");
 	xhci_handle_stopped_cmd_ring(xhci, xhci->current_cmd);
+
+time_out_completed:
 	spin_unlock_irqrestore(&xhci->lock, flags);
 	return;
 }
-- 
2.11.0