[PATCH 5.10 433/518] ACPI: battery: Fix possible crash when unregistering a battery hook

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Armin Wolf <W_Armin@xxxxxx>

[ Upstream commit 76959aff14a0012ad6b984ec7686d163deccdc16 ]

When a battery hook returns an error when adding a new battery, then
the battery hook is automatically unregistered.
However the battery hook provider cannot know that, so it will later
call battery_hook_unregister() on the already unregistered battery
hook, resulting in a crash.

Fix this by using the list head to mark already unregistered battery
hooks as already being unregistered so that they can be ignored by
battery_hook_unregister().

Fixes: fa93854f7a7e ("battery: Add the battery hooking API")
Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
Link: https://patch.msgid.link/20241001212835.341788-3-W_Armin@xxxxxx
Cc: All applicable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/acpi/battery.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index 6d6ad6be58f4a..f9fb092f33a26 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -706,7 +706,7 @@ static void battery_hook_unregister_unlocked(struct acpi_battery_hook *hook)
 	list_for_each_entry(battery, &acpi_battery_list, list) {
 		hook->remove_battery(battery->bat);
 	}
-	list_del(&hook->list);
+	list_del_init(&hook->list);
 
 	pr_info("extension unregistered: %s\n", hook->name);
 }
@@ -714,7 +714,14 @@ static void battery_hook_unregister_unlocked(struct acpi_battery_hook *hook)
 void battery_hook_unregister(struct acpi_battery_hook *hook)
 {
 	mutex_lock(&hook_mutex);
-	battery_hook_unregister_unlocked(hook);
+	/*
+	 * Ignore already unregistered battery hooks. This might happen
+	 * if a battery hook was previously unloaded due to an error when
+	 * adding a new battery.
+	 */
+	if (!list_empty(&hook->list))
+		battery_hook_unregister_unlocked(hook);
+
 	mutex_unlock(&hook_mutex);
 }
 EXPORT_SYMBOL_GPL(battery_hook_unregister);
@@ -724,7 +731,6 @@ void battery_hook_register(struct acpi_battery_hook *hook)
 	struct acpi_battery *battery;
 
 	mutex_lock(&hook_mutex);
-	INIT_LIST_HEAD(&hook->list);
 	list_add(&hook->list, &battery_hook_list);
 	/*
 	 * Now that the driver is registered, we need
-- 
2.43.0







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