usb-serial: fix crash when sub-driver updates firmware

commit 0a3c8549ea7e94d74a41096d42bc6cdf43d183bf upstream.

This patch (as1244) fixes a crash in usb-serial that occurs when a
sub-driver returns a positive value from its attach method, indicating
that new firmware was loaded and the device will disconnect and
reconnect.  The usb-serial core then skips the step of registering the
port devices; when the disconnect occurs, the attempt to unregister
the ports fails dramatically.

This problem shows up with Keyspan devices and it might affect others
as well.

When the attach method returns a positive value, the patch sets
num_ports to 0.  This tells usb_serial_disconnect() not to try
unregistering any of the ports; instead they are cleaned up by
destroy_serial().

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 9fcc272c147eb5dd90472a8fd4c766912b3476e0..579796a1c36b47b93bdc7f1476b0c2f36409e1a2 100644 (file)
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -973,6 +973,7 @@ int usb_serial_probe(struct usb_interface *interface,
                if (retval > 0) {
                        /* quietly accept this device, but don't bind to a
                           serial port as it's about to disappear */
+                       serial->num_ports = 0;
                        goto exit;
                }
        }