Commit 79c4a562 authored by Alexander Usyskin's avatar Alexander Usyskin Committed by Miquel Raynal
Browse files

mtd: call external _get and _put in right order 



MTD provider provides mtd_info object to mtd subsystem.
With kref patch the mtd_info object can be alive after
provider released mtd device.
Fix calling order in _get and _put functions to allow
mtd provider to safely alloc and release mtd object.

Execute:
1) call external _get
2) get_module
3) add internal kref
in the get function and opposite order in the put one.

The _put_device callback should be the last in put
as the master struct memory may be freed in this callback.

Signed-off-by: default avatarAlexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: default avatarMiquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230620131905.648089-3-alexander.usyskin@intel.com
parent 19bfa9eb

drivers/mtd/mtdcore.c

+14 −14
Original line number Diff line number Diff line
@@ -1229,21 +1229,20 @@ int __get_mtd_device(struct mtd_info *mtd) 
	struct mtd_info *master = mtd_get_master(mtd);

	int err;



	if (!try_module_get(master->owner))

		return -ENODEV;



	kref_get(&mtd->refcnt);



	if (master->_get_device) {

		err = master->_get_device(mtd);



		if (err) {

			kref_put(&mtd->refcnt, mtd_device_release);

			module_put(master->owner);

		if (err)

			return err;

	}



	if (!try_module_get(master->owner)) {

		if (master->_put_device)

			master->_put_device(master);

		return -ENODEV;

	}



	kref_get(&mtd->refcnt);



	while (mtd->parent) {

		if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) || mtd->parent != master)

			kref_get(&mtd->parent->refcnt);
@@ -1340,13 +1339,14 @@ void __put_mtd_device(struct mtd_info *mtd) 
		mtd = parent;

	}



	if (master->_put_device)

		master->_put_device(master);

	if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))

		kref_put(&master->refcnt, mtd_device_release);



	module_put(master->owner);



	if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))

		kref_put(&master->refcnt, mtd_device_release);

	/* must be the last as master can be freed in the _put_device */

	if (master->_put_device)

		master->_put_device(master);

}

EXPORT_SYMBOL_GPL(__put_mtd_device);