[PATCH v1] usb: typec: altmodes/displayport: add null pointer check for sysfs nodes

[RD Babiera <rdbabiera@google.com>]

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.

Verify dp drvdata is present in sysfs reads and writes before proceeding.

Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
Cc: stable@vger.kernel.org
Signed-off-by: RD Babiera <rdbabiera@google.com>
---
 drivers/usb/typec/altmodes/displayport.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 5a80776c7255..0423326219d8 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -518,6 +518,9 @@ configuration_store(struct device *dev, struct device_attribute *attr,
 	int con;
 	int ret = 0;
 
+	if (!dp)
+		return -ENODEV;
+
 	con = sysfs_match_string(configurations, buf);
 	if (con < 0)
 		return con;
@@ -563,6 +566,9 @@ static ssize_t configuration_show(struct device *dev,
 	u8 cur;
 	int i;
 
+	if (!dp)
+		return -ENODEV;
+
 	mutex_lock(&dp->lock);
 
 	cap = DP_CAP_CAPABILITY(dp->alt->vdo);
@@ -615,6 +621,9 @@ pin_assignment_store(struct device *dev, struct device_attribute *attr,
 	u32 conf;
 	int ret;
 
+	if (!dp)
+		return -ENODEV;
+
 	ret = sysfs_match_string(pin_assignments, buf);
 	if (ret < 0)
 		return ret;
@@ -666,6 +675,9 @@ static ssize_t pin_assignment_show(struct device *dev,
 	u8 cur;
 	int i;
 
+	if (!dp)
+		return -ENODEV;
+
 	mutex_lock(&dp->lock);
 
 	cur = get_count_order(DP_CONF_GET_PIN_ASSIGN(dp->data.conf));
@@ -698,6 +710,9 @@ static ssize_t hpd_show(struct device *dev, struct device_attribute *attr, char
 {
 	struct dp_altmode *dp = dev_get_drvdata(dev);
 
+	if (!dp)
+		return -ENODEV;
+
 	return sysfs_emit(buf, "%d\n", dp->hpd);
 }
 static DEVICE_ATTR_RO(hpd);

base-commit: f1a27f081c1fa1eeebf38406e45f29636114470f
-- 
2.43.0.429.g432eaa2c6b-goog