mei: vsc: Event notifier fixes

JIRA: https://issues.redhat.com/browse/RHEL-113185

commit 18f14b2
Author: Hans de Goede <hansg@kernel.org>
Date:   Mon Jun 23 10:50:48 2025 +0200

    mei: vsc: Event notifier fixes

    vsc_tp_register_event_cb() can race with vsc_tp_thread_isr(), add a mutex
    to protect against this.

    Fixes: 566f5ca ("mei: Add transport driver for IVSC device")
    Signed-off-by: Hans de Goede <hansg@kernel.org>
    Link: https://lore.kernel.org/r/20250623085052.12347-7-hansg@kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Steve Best <sbest@redhat.com>

Author: sfbest

drivers/misc/mei/vsc-tp.c

@@ -79,9 +79,8 @@ struct vsc_tp {
 
 	vsc_tp_event_cb_t event_notify;
 	void *event_notify_context;
-
-	/* used to protect command download */
-	struct mutex mutex;
+	struct mutex event_notify_mutex;	/* protects event_notify + context */
+	struct mutex mutex;			/* protects command download */
 };
 
 /* GPIO resources */
@@ -113,6 +112,8 @@ static irqreturn_t vsc_tp_thread_isr(int irq, void *data)
 {
 	struct vsc_tp *tp = data;
 
+	guard(mutex)(&tp->event_notify_mutex);
+
 	if (tp->event_notify)
 		tp->event_notify(tp->event_notify_context);
 
@@ -399,6 +400,8 @@ EXPORT_SYMBOL_NS_GPL(vsc_tp_need_read, "VSC_TP");
 int vsc_tp_register_event_cb(struct vsc_tp *tp, vsc_tp_event_cb_t event_cb,
 			    void *context)
 {
+	guard(mutex)(&tp->event_notify_mutex);
+
 	tp->event_notify = event_cb;
 	tp->event_notify_context = context;
 
@@ -499,6 +502,7 @@ static int vsc_tp_probe(struct spi_device *spi)
 		return ret;
 
 	mutex_init(&tp->mutex);
+	mutex_init(&tp->event_notify_mutex);
 
 	/* only one child acpi device */
 	ret = acpi_dev_for_each_child(ACPI_COMPANION(dev),
@@ -523,6 +527,7 @@ static int vsc_tp_probe(struct spi_device *spi)
 err_destroy_lock:
 	free_irq(spi->irq, tp);
 
+	mutex_destroy(&tp->event_notify_mutex);
 	mutex_destroy(&tp->mutex);
 
 	return ret;
@@ -537,6 +542,7 @@ static void vsc_tp_remove(struct spi_device *spi)
 
 	free_irq(spi->irq, tp);
 
+	mutex_destroy(&tp->event_notify_mutex);
 	mutex_destroy(&tp->mutex);
 }