USB: fix error handling in usb_driver_claim_interface()

AlanStern · gregkh · commit bd729f9d67aa · 2018-09-20T12:49:12.000+02:00
The syzbot fuzzing project found a use-after-free bug in the USB
core.  The bug was caused by usbfs not unbinding from an interface
when the USB device file was closed, which led another process to
attempt the unbind later on, after the private data structure had been
deallocated.

The reason usbfs did not unbind the interface at the appropriate time
was because it thought the interface had never been claimed in the
first place.  This was caused by the fact that
usb_driver_claim_interface() does not clean up properly when
device_bind_driver() returns an error.  Although the error code gets
passed back to the caller, the iface-&gt;dev.driver pointer remains set
and iface-&gt;condition remains equal to USB_INTERFACE_BOUND.

This patch adds proper error handling to usb_driver_claim_interface().

Signed-off-by: Alan Stern &lt;stern@rowland.harvard.edu&gt;
Reported-by: syzbot+f84aa7209ccec829536f@syzkaller.appspotmail.com
CC: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
@@ -550,6 +550,21 @@ int usb_driver_claim_interface(struct usb_driver *driver,
 	if (device_is_registered(dev))
 		retval = device_bind_driver(dev);
 
+	if (retval) {
+		dev->driver = NULL;
+		usb_set_intfdata(iface, NULL);
+		iface->needs_remote_wakeup = 0;
+		iface->condition = USB_INTERFACE_UNBOUND;
+
+		/*
+		 * Unbound interfaces are always runtime-PM-disabled
+		 * and runtime-PM-suspended
+		 */
+		if (driver->supports_autosuspend)
+			pm_runtime_disable(dev);
+		pm_runtime_set_suspended(dev);
+	}
+
 	return retval;
 }
 EXPORT_SYMBOL_GPL(usb_driver_claim_interface);
