[patch 3/8] usbserial: fix inconsistent lock state

[akpm@xxxxxxxxxxxxxxxxxxxx]

From: Borislav Petkov <bbpetkov@xxxxxxxx>

In commit acd2a847e7fee7df11817f67dba75a2802793e5d usb_serial_generic_write()
disables interrupts when taking &port->lock which is also taken in
usb_serial_generic_read_bulk_callback() resulting in an inconsistent lock state
due to the latter not disabling interrupts on the local cpu. Fix that by
disabling interrupts in the latter call site also.

Signed-off-by: Borislav Petkov <bbpetkov@xxxxxxxx>
Acked-by: Jiri Kosina <jkosina@xxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 drivers/usb/serial/generic.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff -puN drivers/usb/serial/generic.c~usbserial-fix-inconsistent-lock-state drivers/usb/serial/generic.c
--- a/drivers/usb/serial/generic.c~usbserial-fix-inconsistent-lock-state
+++ a/drivers/usb/serial/generic.c
@@ -327,6 +327,7 @@ void usb_serial_generic_read_bulk_callba
 	struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
 	unsigned char *data = urb->transfer_buffer;
 	int status = urb->status;
+	unsigned long flags;
 
 	dbg("%s - port %d", __FUNCTION__, port->number);
 
@@ -339,11 +340,11 @@ void usb_serial_generic_read_bulk_callba
 	usb_serial_debug_data(debug, &port->dev, __FUNCTION__, urb->actual_length, data);
 
 	/* Throttle the device if requested by tty */
-	spin_lock(&port->lock);
+	spin_lock_irqsave(&port->lock, flags);
 	if (!(port->throttled = port->throttle_req))
 		/* Handle data and continue reading from device */
 		flush_and_resubmit_read_urb(port);
-	spin_unlock(&port->lock);
+	spin_unlock_irqrestore(&port->lock, flags);
 }
 EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);
 
_

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