[PATCH 3.2 038/125] USB: cdc-acm: fix potential urb leak and PM imbalance in write

[Ben Hutchings]

3.2.61-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Johan Hovold <jhovold@xxxxxxxxx>

commit 183a45087d126d126e8dd1d9b2602fc129dff9ad upstream.

Make sure to check return value of autopm get in write() in order to
avoid urb leak and PM counter imbalance on errors.

Fixes: 11ea859d64b6 ("USB: additional power savings for cdc-acm devices
that support remote wakeup")

Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
 - Adjust context
 - Error/status variable is called rc, not stat]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/class/cdc-acm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -191,7 +191,13 @@ static int acm_write_start(struct acm *a
 
 	dev_vdbg(&acm->data->dev, "%s - susp_count %d\n", __func__,
 							acm->susp_count);
-	usb_autopm_get_interface_async(acm->control);
+	rc = usb_autopm_get_interface_async(acm->control);
+	if (rc) {
+		wb->use = 0;
+		spin_unlock_irqrestore(&acm->write_lock, flags);
+		return rc;
+	}
+
 	if (acm->susp_count) {
 		usb_anchor_urb(wb->urb, &acm->delayed);
 		spin_unlock_irqrestore(&acm->write_lock, flags);

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