[PATCH 5.4 044/102] usb: typec: ucsi: displayport: Fix a potential race during registration

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>

commit 081da1325d351ea8804cf74e65263ea120834f33 upstream.

Locking the connector in ucsi_register_displayport() to make
sure that nothing can access the displayport alternate mode
before the function has finished and the alternate mode is
actually ready.

Fixes: af8622f6a585 ("usb: typec: ucsi: Support for DisplayPort alt mode")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200311130006.41288-3-heikki.krogerus@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/typec/ucsi/displayport.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/drivers/usb/typec/ucsi/displayport.c
+++ b/drivers/usb/typec/ucsi/displayport.c
@@ -290,6 +290,8 @@ struct typec_altmode *ucsi_register_disp
 	struct typec_altmode *alt;
 	struct ucsi_dp *dp;
 
+	mutex_lock(&con->lock);
+
 	/* We can't rely on the firmware with the capabilities. */
 	desc->vdo |= DP_CAP_DP_SIGNALING | DP_CAP_RECEPTACLE;
 
@@ -298,12 +300,15 @@ struct typec_altmode *ucsi_register_disp
 	desc->vdo |= all_assignments << 16;
 
 	alt = typec_port_register_altmode(con->port, desc);
-	if (IS_ERR(alt))
+	if (IS_ERR(alt)) {
+		mutex_unlock(&con->lock);
 		return alt;
+	}
 
 	dp = devm_kzalloc(&alt->dev, sizeof(*dp), GFP_KERNEL);
 	if (!dp) {
 		typec_unregister_altmode(alt);
+		mutex_unlock(&con->lock);
 		return ERR_PTR(-ENOMEM);
 	}
 
@@ -316,5 +321,7 @@ struct typec_altmode *ucsi_register_disp
 	alt->ops = &ucsi_displayport_ops;
 	typec_altmode_set_drvdata(alt, dp);
 
+	mutex_unlock(&con->lock);
+
 	return alt;
 }