linux-kernel - [PATCH v2] usb: typec: altmodes/displayport: create sysfs nodes after assigning driver data

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Date: Mon, 26 Feb 2024 23:42:29 +0000
From: RD Babiera <rdbabiera@...gle.com>
To: rdbabiera@...gle.com, heikki.krogerus@...ux.intel.com, 
	gregkh@...uxfoundation.org
Cc: badhri@...gle.com, linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: [PATCH v2] usb: typec: altmodes/displayport: create sysfs nodes after
 assigning driver data

The DisplayPort driver's sysfs nodes may be present to the userspace before
typec_altmode_set_drvdata() completes in dp_altmode_probe. This means that
a sysfs read can trigger a NULL pointer error by deferencing dp->hpd in
hpd_show or dp->lock in pin_assignment_show, as dev_get_drvdata() returns
NULL in those cases.

Create sysfs nodes after typec_altmode_set_drvdata call.

Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
Cc: stable@...r.kernel.org
Signed-off-by: RD Babiera <rdbabiera@...gle.com>
---
Changes from v1:
* Moved sysfs node creation instead of NULL checking dev_get_drvdata().
---
 drivers/usb/typec/altmodes/displayport.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 5a80776c7255..5bbdd2c04237 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -731,10 +731,6 @@ int dp_altmode_probe(struct typec_altmode *alt)
 	      DP_CAP_PIN_ASSIGN_DFP_D(alt->vdo)))
 		return -ENODEV;
 
-	ret = sysfs_create_group(&alt->dev.kobj, &dp_altmode_group);
-	if (ret)
-		return ret;
-
 	dp = devm_kzalloc(&alt->dev, sizeof(*dp), GFP_KERNEL);
 	if (!dp)
 		return -ENOMEM;
@@ -766,6 +762,10 @@ int dp_altmode_probe(struct typec_altmode *alt)
 	if (plug)
 		typec_altmode_set_drvdata(plug, dp);
 
+	ret = sysfs_create_group(&alt->dev.kobj, &dp_altmode_group);
+	if (ret)
+		return ret;
+
 	dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
 	schedule_work(&dp->work);
 

base-commit: a560a5672826fc1e057068bda93b3d4c98d037a2
-- 
2.44.0.rc1.240.g4c46232300-goog