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

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Message-ID: <20240424014821.4154159-2-jthies@google.com>
Date: Wed, 24 Apr 2024 01:48:18 +0000
From: Jameson Thies <jthies@...gle.com>
To: heikki.krogerus@...ux.intel.com, linux-usb@...r.kernel.org
Cc: jthies@...gle.com, pmalani@...omium.org, bleung@...gle.com, 
	abhishekpandit@...omium.org, andersson@...nel.org, 
	dmitry.baryshkov@...aro.org, fabrice.gasnier@...s.st.com, 
	gregkh@...uxfoundation.org, hdegoede@...hat.com, neil.armstrong@...aro.org, 
	rajaram.regupathy@...el.com, saranya.gopal@...el.com, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/4] usb: typec: ucsi: Fix null deref in trace

From: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>

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@...gle.com>
Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
---
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