Commit e9714c22 authored by Alexander Usyskin's avatar Alexander Usyskin Committed by Miquel Raynal
Browse files

mtd: fix use-after-free in mtd release 



I case of partition device_unregister() in mtd_device_release()
calls mtd_release() which frees mtd_info structure for partition.
All code after device_unregister in mtd_device_release thus
uses already freed memory.

Move part of code to mtd_release() and restict mtd->dev cleanup
to non-partion object.
For partition object such cleanup have no sense as partition
mtd_info is removed.

Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Fixes: 19bfa9eb ("mtd: use refcount to prevent corruption")
Reviewed-by: default avatarTomas Winkler <tomas.winkler@intel.com>
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/20230731115836.542747-1-alexander.usyskin@intel.com
parent d2236f62

drivers/mtd/mtdcore.c

+11 −5
Original line number Diff line number Diff line
@@ -93,6 +93,9 @@ static void mtd_release(struct device *dev) 
	struct mtd_info *mtd = dev_get_drvdata(dev);

	dev_t index = MTD_DEVT(mtd->index);



	idr_remove(&mtd_idr, mtd->index);

	of_node_put(mtd_get_of_node(mtd));



	if (mtd_is_partition(mtd))

		release_mtd_partition(mtd);
@@ -103,6 +106,7 @@ static void mtd_release(struct device *dev) 
static void mtd_device_release(struct kref *kref)

{

	struct mtd_info *mtd = container_of(kref, struct mtd_info, refcnt);

	bool is_partition = mtd_is_partition(mtd);



	debugfs_remove_recursive(mtd->dbg.dfs_dir);
@@ -111,12 +115,14 @@ static void mtd_device_release(struct kref *kref) 


	device_unregister(&mtd->dev);



	/* Clear dev so mtd can be safely re-registered later if desired */

	/*

	 *  Clear dev so mtd can be safely re-registered later if desired.

	 *  Should not be done for partition,

	 *  as it was already destroyed in device_unregister().

	 */

	if (!is_partition)

		memset(&mtd->dev, 0, sizeof(mtd->dev));



	idr_remove(&mtd_idr, mtd->index);

	of_node_put(mtd_get_of_node(mtd));



	module_put(THIS_MODULE);

}