[PATCH v13 01/10] power: reset: reboot-mode: Synchronize list traversal

[Shivendra Pratap]

List traversals must be synchronized to prevent race conditions
and data corruption. The reboot-mode list is not protected by a
lock currently, which can lead to concurrent access and race.

Introduce a mutex lock to guard all operations on the reboot-mode
list and ensure thread-safe access. The change prevents unsafe
concurrent access on reboot-mode list.

Signed-off-by: Shivendra Pratap <shivendra.pratap at oss.qualcomm.com>
---
 drivers/power/reset/reboot-mode.c | 24 ++++++++++++++++++++----
 include/linux/reboot-mode.h       |  4 ++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
index fba53f638da04655e756b5f8b7d2d666d1379535..42bb99128ed3846d4bff62416dc31135ddeaeb90 100644
--- a/drivers/power/reset/reboot-mode.c
+++ b/drivers/power/reset/reboot-mode.c
@@ -29,9 +29,14 @@ static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
 	if (!cmd)
 		cmd = normal;
 
-	list_for_each_entry(info, &reboot->head, list)
-		if (!strcmp(info->mode, cmd))
+	mutex_lock(&reboot->rb_lock);
+	list_for_each_entry(info, &reboot->head, list) {
+		if (!strcmp(info->mode, cmd)) {
+			mutex_unlock(&reboot->rb_lock);
 			return info->magic;
+		}
+	}
+	mutex_unlock(&reboot->rb_lock);
 
 	/* try to match again, replacing characters impossible in DT */
 	if (strscpy(cmd_, cmd, sizeof(cmd_)) == -E2BIG)
@@ -41,9 +46,14 @@ static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
 	strreplace(cmd_, ',', '-');
 	strreplace(cmd_, '/', '-');
 
-	list_for_each_entry(info, &reboot->head, list)
-		if (!strcmp(info->mode, cmd_))
+	mutex_lock(&reboot->rb_lock);
+	list_for_each_entry(info, &reboot->head, list) {
+		if (!strcmp(info->mode, cmd_)) {
+			mutex_unlock(&reboot->rb_lock);
 			return info->magic;
+		}
+	}
+	mutex_unlock(&reboot->rb_lock);
 
 	return 0;
 }
@@ -77,7 +87,9 @@ int reboot_mode_register(struct reboot_mode_driver *reboot)
 	int ret;
 
 	INIT_LIST_HEAD(&reboot->head);
+	mutex_init(&reboot->rb_lock);
 
+	mutex_lock(&reboot->rb_lock);
 	for_each_property_of_node(np, prop) {
 		if (strncmp(prop->name, PREFIX, len))
 			continue;
@@ -113,12 +125,14 @@ int reboot_mode_register(struct reboot_mode_driver *reboot)
 	reboot->reboot_notifier.notifier_call = reboot_mode_notify;
 	register_reboot_notifier(&reboot->reboot_notifier);
 
+	mutex_unlock(&reboot->rb_lock);
 	return 0;
 
 error:
 	list_for_each_entry(info, &reboot->head, list)
 		kfree_const(info->mode);
 
+	mutex_unlock(&reboot->rb_lock);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(reboot_mode_register);
@@ -133,8 +147,10 @@ int reboot_mode_unregister(struct reboot_mode_driver *reboot)
 
 	unregister_reboot_notifier(&reboot->reboot_notifier);
 
+	mutex_lock(&reboot->rb_lock);
 	list_for_each_entry(info, &reboot->head, list)
 		kfree_const(info->mode);
+	mutex_unlock(&reboot->rb_lock);
 
 	return 0;
 }
diff --git a/include/linux/reboot-mode.h b/include/linux/reboot-mode.h
index 4a2abb38d1d612ec0fdf05eb18c98b210f631b7f..b73f80708197677db8dc2e43affc519782b7146e 100644
--- a/include/linux/reboot-mode.h
+++ b/include/linux/reboot-mode.h
@@ -2,11 +2,15 @@
 #ifndef __REBOOT_MODE_H__
 #define __REBOOT_MODE_H__
 
+#include <linux/mutex.h>
+
 struct reboot_mode_driver {
 	struct device *dev;
 	struct list_head head;
 	int (*write)(struct reboot_mode_driver *reboot, unsigned int magic);
 	struct notifier_block reboot_notifier;
+	/*Protects access to reboot mode list*/
+	struct mutex rb_lock;
 };
 
 int reboot_mode_register(struct reboot_mode_driver *reboot);

-- 
2.34.1