[PATCH 5.5 049/119] usb: typec: ucsi: displayport: Fix NULL pointer dereference

[Greg Kroah-Hartman]

From: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>

commit d16e7b62c5adcd13832c6b0ba364c3468d21b856 upstream.

If the registration of the DisplayPort was not successful,
or if the port does not support DisplayPort alt mode in the
first place, the function ucsi_displayport_remove_partner()
will fail with NULL pointer dereference when it attempts to
access the driver data.

Adding a check to the function to make sure there really is
driver data for the device before modifying it.

Fixes: af8622f6a585 ("usb: typec: ucsi: Support for DisplayPort alt mode")
Reported-by: Andrea Gagliardi La Gala <andrea.lagala@xxxxxxxxx>
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206365
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200311130006.41288-2-heikki.krogerus@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/typec/ucsi/displayport.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/usb/typec/ucsi/displayport.c
+++ b/drivers/usb/typec/ucsi/displayport.c
@@ -271,6 +271,9 @@ void ucsi_displayport_remove_partner(str
 		return;
 
 	dp = typec_altmode_get_drvdata(alt);
+	if (!dp)
+		return;
+
 	dp->data.conf = 0;
 	dp->data.status = 0;
 	dp->initialized = false;