usb: typec: ucsi: Only check the contract if there is a connection

The driver must make sure there is an actual connection
before checking details about the USB Power Delivery
contract. Those details are not valid unless there is a
connection.

This fixes NULL pointer dereference that is caused by an
attempt to register bogus partner alternate mode that the
firmware on some platform may report before the actual
connection.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=215117
Fixes: 6cbe4b2 ("usb: typec: ucsi: Check the partner alt modes always if there is PD contract")
Reported-by: Chris Hixon <[email protected]>
Signed-off-by: Heikki Krogerus <[email protected]>
Link: https://lore.kernel.org/r/[email protected]/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Heikki Krogerus

drivers/usb/typec/ucsi/ucsi.c

@@ -1150,7 +1150,9 @@ static int ucsi_register_port(struct ucsi *ucsi, int index)
 		ret = 0;
 	}
 
-	if (UCSI_CONSTAT_PWR_OPMODE(con->status.flags) == UCSI_CONSTAT_PWR_OPMODE_PD) {
+	if (con->partner &&
+	    UCSI_CONSTAT_PWR_OPMODE(con->status.flags) ==
+	    UCSI_CONSTAT_PWR_OPMODE_PD) {
 		ucsi_get_src_pdos(con);
 		ucsi_check_altmodes(con);
 	}