[PATCH 4.16 131/196] mmc: core: Prevent bus reference leak in mmc_blk_init()

[Greg Kroah-Hartman]

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

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

From: Alexander Kappner <agk@xxxxxxxxxxx>

commit d0a0852b9f81cf5f793bf2eae7336ed40a1a1815 upstream.

Upon module load, mmc_block allocates a bus with bus_registeri() in
mmc_blk_init(). This reference never gets freed during module unload, which
leads to subsequent re-insertions of the module fails and a WARN() splat is
triggered.

Fix the bug by dropping the reference for the bus in mmc_blk_exit().

Signed-off-by: Alexander Kappner <agk@xxxxxxxxxxx>
Fixes: 97548575bef3 ("mmc: block: Convert RPMB to a character device")
Cc: <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/mmc/core/block.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -3087,6 +3087,7 @@ static void __exit mmc_blk_exit(void)
 	mmc_unregister_driver(&mmc_driver);
 	unregister_blkdev(MMC_BLOCK_MAJOR, "mmc");
 	unregister_chrdev_region(mmc_rpmb_devt, MAX_DEVICES);
+	bus_unregister(&mmc_rpmb_bus_type);
 }
 
 module_init(mmc_blk_init);