[ 34/91] USB: cdc-wdm: cannot use dev_printk when device is gone

[Greg KH]

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bjørn Mork <bjorn@xxxxxxx>

commit 6b0b79d38806481c1c8fffa7c5842f3c83679a42 upstream.

We cannot dereference a removed USB interface for
dev_printk. Use pr_debug instead where necessary.

Flush errors are expected if device is unplugged and are
therefore best ingored at this point.

Move the kill_urbs() call in wdm_release with dev_dbg()
for the non disconnect, as we know it has already been
called if WDM_DISCONNECTING is set.  This does not
actually fix anything, but keeps the code more consistent.

Cc: Oliver Neukum <oliver@xxxxxxxxxx>
Signed-off-by: Bjørn Mork <bjorn@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/class/cdc-wdm.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -530,7 +530,9 @@ static int wdm_flush(struct file *file,
 	struct wdm_device *desc = file->private_data;
 
 	wait_event(desc->wait, !test_bit(WDM_IN_USE, &desc->flags));
-	if (desc->werr < 0)
+
+	/* cannot dereference desc->intf if WDM_DISCONNECTING */
+	if (desc->werr < 0 && !test_bit(WDM_DISCONNECTING, &desc->flags))
 		dev_err(&desc->intf->dev, "Error in flush path: %d\n",
 			desc->werr);
 
@@ -621,12 +623,15 @@ static int wdm_release(struct inode *ino
 	mutex_unlock(&desc->wlock);
 
 	if (!desc->count) {
-		dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
-		kill_urbs(desc);
-		if (!test_bit(WDM_DISCONNECTING, &desc->flags))
+		if (!test_bit(WDM_DISCONNECTING, &desc->flags)) {
+			dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
+			kill_urbs(desc);
 			desc->manage_power(desc->intf, 0);
-		else
+		} else {
+			/* must avoid dev_printk here as desc->intf is invalid */
+			pr_debug(KBUILD_MODNAME " %s: device gone - cleaning up\n", __func__);
 			cleanup(desc);
+		}
 	}
 	mutex_unlock(&wdm_mutex);
 	return 0;


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