[v2] mtd: fix use-after-free in mtd release
Commit Message
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: 19bfa9ebebb5 ("mtd: use refcount to prevent corruption")
Reviewed-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
---
V2: Fix commit messsge wording
---
drivers/mtd/mtdcore.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
Comments
On Mon, 2023-07-31 at 11:58:36 UTC, Alexander Usyskin wrote:
> 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: 19bfa9ebebb5 ("mtd: use refcount to prevent corruption")
> Reviewed-by: Tomas Winkler <tomas.winkler@intel.com>
> 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
@@ -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);
@@ -111,11 +115,13 @@ static void mtd_device_release(struct kref *kref)
device_unregister(&mtd->dev);
- /* Clear dev so mtd can be safely re-registered later if desired */
- memset(&mtd->dev, 0, sizeof(mtd->dev));
-
- idr_remove(&mtd_idr, mtd->index);
- of_node_put(mtd_get_of_node(mtd));
+ /*
+ * 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));
module_put(THIS_MODULE);
}