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

Ben Hutchings
2019-12-17T00:56:52Z

From: Johan Hovold <johan@kernel.org>

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@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191015175522.18490-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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;