[PATCH 3.16 070/136] USB: usblp: fix use-after-free on disconnect

[Ben Hutchings]

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

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

From: Johan Hovold <johan@xxxxxxxxxx>

commit 7a759197974894213621aa65f0571b51904733d6 upstream.

A recent commit addressing a runtime PM use-count regression, introduced
a use-after-free by not making sure we held a reference to the struct
usb_interface for the lifetime of the driver data.

Fixes: 9a31535859bf ("USB: usblp: fix runtime PM after driver unbind")
Reported-by: syzbot+cd24df4d075c319ebfc5@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20191015175522.18490-1-johan@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/class/usblp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -447,6 +447,7 @@ static void usblp_cleanup(struct usblp *
 	kfree(usblp->readbuf);
 	kfree(usblp->device_id_string);
 	kfree(usblp->statusbuf);
+	usb_put_intf(usblp->intf);
 	kfree(usblp);
 }
 
@@ -1104,7 +1105,7 @@ static int usblp_probe(struct usb_interf
 	init_waitqueue_head(&usblp->wwait);
 	init_usb_anchor(&usblp->urbs);
 	usblp->ifnum = intf->cur_altsetting->desc.bInterfaceNumber;
-	usblp->intf = intf;
+	usblp->intf = usb_get_intf(intf);
 
 	/* Malloc device ID string buffer to the largest expected length,
 	 * since we can re-query it on an ioctl and a dynamic string
@@ -1193,6 +1194,7 @@ abort:
 	kfree(usblp->readbuf);
 	kfree(usblp->statusbuf);
 	kfree(usblp->device_id_string);
+	usb_put_intf(usblp->intf);
 	kfree(usblp);
 abort_ret:
 	return retval;