[PATCH 3/5] mtd: maps: physmap: fix reference leak on failed device registration

[Vastargazing]

When platform_device_register() fails in physmap_init(), the embedded
struct device has already been initialized by device_initialize() inside
platform_device_register(). The error path unregisters the driver but
returns without dropping the device reference:

  physmap_init()
    -> platform_device_register(&physmap_flash)
       -> device_initialize(&physmap_flash.dev)   /* kref = 1 */
       -> platform_device_add(&physmap_flash)     /* fails */
    <- platform_driver_unregister() called, but kref still 1

Per platform_device_register() kernel-doc:

  NOTE: _Never_ directly free @pdev after calling this function, even if
  it returned an error! Always use platform_device_put() to give up the
  reference initialised in this function instead.

Fix this by calling platform_device_put() before unregistering the driver.

Fixes: 73566edf9b91 ("[MTD] Convert physmap to platform driver")
Cc: stable at vger.kernel.org
Assisted-by: GitHub Copilot (Claude Sonnet 4.5)
Signed-off-by: Vastargazing <vebohr at gmail.com>
---
 drivers/mtd/maps/physmap-core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/maps/physmap-core.c b/drivers/mtd/maps/physmap-core.c
index dcda7685fc99..45d79ca622c1 100644
--- a/drivers/mtd/maps/physmap-core.c
+++ b/drivers/mtd/maps/physmap-core.c
@@ -654,8 +654,10 @@ static int __init physmap_init(void)
 #ifdef CONFIG_MTD_PHYSMAP_COMPAT
 	if (err == 0) {
 		err = platform_device_register(&physmap_flash);
-		if (err)
+		if (err) {
+			platform_device_put(&physmap_flash);
 			platform_driver_unregister(&physmap_flash_driver);
+		}
 	}
 #endif
 
-- 
2.51.0