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

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

From: Alexander Kappner <[email protected]>

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 <[email protected]>
Fixes: 97548575bef3 ("mmc: block: Convert RPMB to a character device")
Cc: <[email protected]>
Reviewed-by: Shawn Lin <[email protected]>
Signed-off-by: Ulf Hansson <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 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);


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