diff mbox series

[2/2] mtd: call external _get and _put in right order

Message ID 20230620131905.648089-3-alexander.usyskin@intel.com
State Accepted
Headers show
Series [1/2] mtd: use refcount to prevent corruption | expand

Commit Message

Usyskin, Alexander June 20, 2023, 1:19 p.m. UTC 
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: Alexander Usyskin <alexander.usyskin@intel.com>
---
 drivers/mtd/mtdcore.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

Comments

Miquel Raynal July 12, 2023, 2:13 p.m. UTC | #1 
On Tue, 2023-06-20 at 13:19:05 UTC, Alexander Usyskin wrote:
> 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: Alexander Usyskin <alexander.usyskin@intel.com>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel
diff mbox series

Patch

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 84bd1878367d..a5bc60013edf 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -1227,21 +1227,20 @@  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);
@@ -1338,13 +1337,14 @@  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);