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authorJiri Slaby <jslaby@suse.cz>2019-05-17 06:38:43 +0200
committerJiri Slaby <jslaby@suse.cz>2019-05-17 06:38:46 +0200
commit02b2df97c96578f7aab60d8f46c41c159535980c (patch)
treed3f0816944f2f72ce626280a288c6c5b7e2ece89
parentb4d23dcfe358a076e42c578fad1f6b844fa40723 (diff)
USB: serial: fix unthrottle races (bnc#1012628).
-rw-r--r--drivers/usb/serial/generic.c39
1 files changed, 32 insertions, 7 deletions
diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 2274d9625f63..0fff4968ea1b 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -376,6 +376,7 @@ void usb_serial_generic_read_bulk_callback(struct urb *urb)
struct usb_serial_port *port = urb->context;
unsigned char *data = urb->transfer_buffer;
unsigned long flags;
+ bool stopped = false;
int status = urb->status;
int i;
@@ -383,33 +384,51 @@ void usb_serial_generic_read_bulk_callback(struct urb *urb)
if (urb == port->read_urbs[i])
break;
}
- set_bit(i, &port->read_urbs_free);
dev_dbg(&port->dev, "%s - urb %d, len %d\n", __func__, i,
urb->actual_length);
switch (status) {
case 0:
+ usb_serial_debug_data(&port->dev, __func__, urb->actual_length,
+ data);
+ port->serial->type->process_read_urb(urb);
break;
case -ENOENT:
case -ECONNRESET:
case -ESHUTDOWN:
dev_dbg(&port->dev, "%s - urb stopped: %d\n",
__func__, status);
- return;
+ stopped = true;
+ break;
case -EPIPE:
dev_err(&port->dev, "%s - urb stopped: %d\n",
__func__, status);
- return;
+ stopped = true;
+ break;
default:
dev_dbg(&port->dev, "%s - nonzero urb status: %d\n",
__func__, status);
- goto resubmit;
+ break;
}
- usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);
- port->serial->type->process_read_urb(urb);
+ /*
+ * Make sure URB processing is done before marking as free to avoid
+ * racing with unthrottle() on another CPU. Matches the barriers
+ * implied by the test_and_clear_bit() in
+ * usb_serial_generic_submit_read_urb().
+ */
+ smp_mb__before_atomic();
+ set_bit(i, &port->read_urbs_free);
+ /*
+ * Make sure URB is marked as free before checking the throttled flag
+ * to avoid racing with unthrottle() on another CPU. Matches the
+ * smp_mb() in unthrottle().
+ */
+ smp_mb__after_atomic();
+
+ if (stopped)
+ return;
-resubmit:
/* Throttle the device if requested by tty */
spin_lock_irqsave(&port->lock, flags);
port->throttled = port->throttle_req;
@@ -484,6 +503,12 @@ void usb_serial_generic_unthrottle(struct tty_struct *tty)
port->throttled = port->throttle_req = 0;
spin_unlock_irq(&port->lock);
+ /*
+ * Matches the smp_mb__after_atomic() in
+ * usb_serial_generic_read_bulk_callback().
+ */
+ smp_mb();
+
if (was_throttled)
usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
}