[PATCH v2 1/4] usb: typec: ucsi: Fix null deref in trace

[Jameson Thies]

From: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx>

ucsi_register_altmode checks IS_ERR on returned pointer and treats
NULL as valid. This results in a null deref when
trace_ucsi_register_altmode is called. Return an error from
ucsi_register_displayport when it is not supported and register the
altmode with typec_port_register_altmode.

Reviewed-by: Jameson Thies <jthies@xxxxxxxxxx>
Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx>
---
Changes in V2:
- Checks for error response from ucsi_register_displayport when
registering DisplayPort alternate mode.

 drivers/usb/typec/ucsi/ucsi.c | 3 +++
 drivers/usb/typec/ucsi/ucsi.h | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index cb52e7b0a2c5c..f3b413f94fd28 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -361,6 +361,9 @@ static int ucsi_register_altmode(struct ucsi_connector *con,
 		switch (desc->svid) {
 		case USB_TYPEC_DP_SID:
 			alt = ucsi_register_displayport(con, override, i, desc);
+			if (IS_ERR(alt) && PTR_ERR(alt) == -EOPNOTSUPP)
+				alt = typec_port_register_altmode(con->port, desc);
+
 			break;
 		case USB_TYPEC_NVIDIA_VLINK_SID:
 			if (desc->vdo == USB_TYPEC_NVIDIA_VLINK_DBG_VDO)
diff --git a/drivers/usb/typec/ucsi/ucsi.h b/drivers/usb/typec/ucsi/ucsi.h
index c4d103db9d0f8..c663dce0659ee 100644
--- a/drivers/usb/typec/ucsi/ucsi.h
+++ b/drivers/usb/typec/ucsi/ucsi.h
@@ -496,7 +496,7 @@ ucsi_register_displayport(struct ucsi_connector *con,
 			  bool override, int offset,
 			  struct typec_altmode_desc *desc)
 {
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 static inline void
-- 
2.44.0.769.g3c40516874-goog