register_platform_devices() registers the battery, LED, and watchdog
platform devices in sequence. If LED registration fails, the battery
device remains registered. If watchdog registration fails, the LED and
battery devices remain registered.

These failure paths leave successful platform_device_register_data()
calls without the matching platform_device_unregister() calls.

Add an unwind ladder to unregister previously registered platform
devices in reverse order before returning the registration error.

The issue was identified by a static analysis tool I developed and
confirmed by manual review.

Fixes: dd123e62bded ("platform/x86: simatic-ipc: add main driver for Siemens devices")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
v2:
  - Use an unwind ladder to unregister previously registered platform
    devices in reverse order, as suggested by Dan Carpenter.

 drivers/platform/x86/siemens/simatic-ipc.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/siemens/simatic-ipc.c b/drivers/platform/x86/siemens/simatic-ipc.c
index 7039874d8f11..4a4509fc9263 100644
--- a/drivers/platform/x86/siemens/simatic-ipc.c
+++ b/drivers/platform/x86/siemens/simatic-ipc.c
@@ -92,6 +92,7 @@ static int register_platform_devices(u32 station_id)
 	u8 wdtmode = SIMATIC_IPC_DEVICE_NONE;
 	u8 battmode = SIMATIC_IPC_DEVICE_NONE;
 	char *pdevname;
+	int ret;
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(device_modes); i++) {
@@ -139,8 +140,10 @@ static int register_platform_devices(u32 station_id)
 				pdevname, PLATFORM_DEVID_NONE,
 				&platform_data,
 				sizeof(struct simatic_ipc_platform));
-		if (IS_ERR(ipc_led_platform_device))
-			return PTR_ERR(ipc_led_platform_device);
+		if (IS_ERR(ipc_led_platform_device)) {
+			ret = PTR_ERR(ipc_led_platform_device);
+			goto err_unregister_batt;
+		}
 
 		pr_debug("device=%s created\n",
 			 ipc_led_platform_device->name);
@@ -153,8 +156,10 @@ static int register_platform_devices(u32 station_id)
 				KBUILD_MODNAME "_wdt", PLATFORM_DEVID_NONE,
 				&platform_data,
 				sizeof(struct simatic_ipc_platform));
-		if (IS_ERR(ipc_wdt_platform_device))
-			return PTR_ERR(ipc_wdt_platform_device);
+		if (IS_ERR(ipc_wdt_platform_device)) {
+			ret = PTR_ERR(ipc_wdt_platform_device);
+			goto err_unregister_led;
+		}
 
 		pr_debug("device=%s created\n",
 			 ipc_wdt_platform_device->name);
@@ -169,6 +174,14 @@ static int register_platform_devices(u32 station_id)
 	}
 
 	return 0;
+
+err_unregister_led:
+	if (ledmode != SIMATIC_IPC_DEVICE_NONE)
+		platform_device_unregister(ipc_led_platform_device);
+err_unregister_batt:
+	if (battmode != SIMATIC_IPC_DEVICE_NONE)
+		platform_device_unregister(ipc_batt_platform_device);
+	return ret;
 }
 
 static void request_additional_modules(u32 station_id)
-- 
2.43.0