New subject: [PATCH 5.15.y] usb: typec: ucsi: displayport: Fix deadlock

12 May 2025

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 364618c89d4c57c85e5fc51a2446cd939bf57802
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025051221-pacifist-liability-19cf@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 364618c89d4c57c85e5fc51a2446cd939bf57802 Mon Sep 17 00:00:00 2001
From: Andrei Kuchynski akuchynski@chromium.org
Date: Thu, 24 Apr 2025 08:44:28 +0000
Subject: [PATCH] usb: typec: ucsi: displayport: Fix deadlock
This patch introduces the ucsi_con_mutex_lock / ucsi_con_mutex_unlock
functions to the UCSI driver. ucsi_con_mutex_lock ensures the connector
mutex is only locked if a connection is established and the partner pointer
is valid. This resolves a deadlock scenario where
ucsi_displayport_remove_partner holds con->mutex waiting for
dp_altmode_work to complete while dp_altmode_work attempts to acquire it.
Cc: stable stable@kernel.org
Fixes: af8622f6a585 ("usb: typec: ucsi: Support for DisplayPort alt mode")
Signed-off-by: Andrei Kuchynski akuchynski@chromium.org
Reviewed-by: Heikki Krogerus heikki.krogerus@linux.intel.com
Link: https://lore.kernel.org/r/20250424084429.3220757-2-akuchynski@chromium.org
Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/usb/typec/ucsi/displayport.c b/drivers/usb/typec/ucsi/displayport.c
index 420af5139c70..acd053d4e38c 100644
--- a/drivers/usb/typec/ucsi/displayport.c
+++ b/drivers/usb/typec/ucsi/displayport.c
@@ -54,7 +54,8 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
    u8 cur = 0;
    int ret;
-	mutex_lock(&dp->con->lock);
+	if (!ucsi_con_mutex_lock(dp->con))
+		return -ENOTCONN;
if (!dp->override && dp->initialized) {
    	const struct typec_altmode *p = typec_altmode_get_partner(alt);
@@ -100,7 +101,7 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
    schedule_work(&dp->work);
    ret = 0;
 err_unlock:
-	mutex_unlock(&dp->con->lock);
+	ucsi_con_mutex_unlock(dp->con);
return ret;
 }
@@ -112,7 +113,8 @@ static int ucsi_displayport_exit(struct typec_altmode *alt)
    u64 command;
    int ret = 0;
-	mutex_lock(&dp->con->lock);
+	if (!ucsi_con_mutex_lock(dp->con))
+		return -ENOTCONN;
if (!dp->override) {
    	const struct typec_altmode *p = typec_altmode_get_partner(alt);
@@ -144,7 +146,7 @@ static int ucsi_displayport_exit(struct typec_altmode *alt)
    schedule_work(&dp->work);
out_unlock:
-	mutex_unlock(&dp->con->lock);
+	ucsi_con_mutex_unlock(dp->con);
return ret;
 }
@@ -202,20 +204,21 @@ static int ucsi_displayport_vdm(struct typec_altmode *alt,
    int cmd = PD_VDO_CMD(header);
    int svdm_version;
-	mutex_lock(&dp->con->lock);
+	if (!ucsi_con_mutex_lock(dp->con))
+		return -ENOTCONN;
if (!dp->override && dp->initialized) {
    	const struct typec_altmode *p = typec_altmode_get_partner(alt);
dev_warn(&p->dev,
    		 "firmware doesn't support alternate mode overriding\n");
-		mutex_unlock(&dp->con->lock);
+		ucsi_con_mutex_unlock(dp->con);
    	return -EOPNOTSUPP;
    }
svdm_version = typec_altmode_get_svdm_version(alt);
    if (svdm_version < 0) {
-		mutex_unlock(&dp->con->lock);
+		ucsi_con_mutex_unlock(dp->con);
    	return svdm_version;
    }
@@ -259,7 +262,7 @@ static int ucsi_displayport_vdm(struct typec_altmode *alt,
    	break;
    }
-	mutex_unlock(&dp->con->lock);
+	ucsi_con_mutex_unlock(dp->con);
return 0;
 }
diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index e8c7e9dc4930..01ce858a1a2b 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1922,6 +1922,40 @@ void ucsi_set_drvdata(struct ucsi *ucsi, void *data)
 }
 EXPORT_SYMBOL_GPL(ucsi_set_drvdata);
+/**
+ * ucsi_con_mutex_lock - Acquire the connector mutex
+ * @con: The connector interface to lock
+ *
+ * Returns true on success, false if the connector is disconnected
+ */
+bool ucsi_con_mutex_lock(struct ucsi_connector *con)
+{
+	bool mutex_locked = false;
+	bool connected = true;
+
+	while (connected && !mutex_locked) {
+		mutex_locked = mutex_trylock(&con->lock) != 0;
+		connected = UCSI_CONSTAT(con, CONNECTED);
+		if (connected && !mutex_locked)
+			msleep(20);
+	}
+
+	connected = connected && con->partner;
+	if (!connected && mutex_locked)
+		mutex_unlock(&con->lock);
+
+	return connected;
+}
+
+/**
+ * ucsi_con_mutex_unlock - Release the connector mutex
+ * @con: The connector interface to unlock
+ */
+void ucsi_con_mutex_unlock(struct ucsi_connector *con)
+{
+	mutex_unlock(&con->lock);
+}
+
 /**
  * ucsi_create - Allocate UCSI instance
  * @dev: Device interface to the PPM (Platform Policy Manager)
diff --git a/drivers/usb/typec/ucsi/ucsi.h b/drivers/usb/typec/ucsi/ucsi.h
index 3a2c1762bec1..9c5278a0c5d4 100644
--- a/drivers/usb/typec/ucsi/ucsi.h
+++ b/drivers/usb/typec/ucsi/ucsi.h
@@ -94,6 +94,8 @@ int ucsi_register(struct ucsi *ucsi);
 void ucsi_unregister(struct ucsi *ucsi);
 void *ucsi_get_drvdata(struct ucsi *ucsi);
 void ucsi_set_drvdata(struct ucsi *ucsi, void *data);
+bool ucsi_con_mutex_lock(struct ucsi_connector *con);
+void ucsi_con_mutex_unlock(struct ucsi_connector *con);
void ucsi_connector_change(struct ucsi *ucsi, u8 num);

    

FAILED: patch "[PATCH] usb: typec: ucsi: displayport: Fix deadlock" failed to apply to 5.15-stable tree