[PATCH] serial: 8250_exar_st16c554: fix reference leak on failed device registration

[Guangshuo Li]

When platform_device_register() fails in exar_init(), the embedded
struct device in exar_device has already been initialized by
device_initialize(), but the failure path returns the error without
dropping the device reference for the current platform device:

  exar_init()
    -> platform_device_register(&exar_device)
       -> device_initialize(&exar_device.dev)
       -> setup_pdev_dma_masks(&exar_device)
       -> platform_device_add(&exar_device)

This leads to a reference leak when platform_device_register() fails.
Fix this by calling platform_device_put() before returning the error.

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

Fixes: e0980dafa329d ("[PATCH] Exar quad port serial")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
---
 drivers/tty/serial/8250/8250_exar_st16c554.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_exar_st16c554.c b/drivers/tty/serial/8250/8250_exar_st16c554.c
index 933811ebfaac..b2c37f0c52aa 100644
--- a/drivers/tty/serial/8250/8250_exar_st16c554.c
+++ b/drivers/tty/serial/8250/8250_exar_st16c554.c
@@ -30,7 +30,13 @@ static struct platform_device exar_device = {
 
 static int __init exar_init(void)
 {
-	return platform_device_register(&exar_device);
+	int ret;
+
+	ret = platform_device_register(&exar_device);
+	if (ret)
+		platform_device_put(&exar_device);
+
+	return ret;
 }
 
 module_init(exar_init);
-- 
2.43.0