[PATCH] rnbd-clt: fix use-after-free on device sysfs creation failure

[Shuangpeng Bai <shuangpeng.kernel@gmail.com>]

rnbd_clt_add_dev_kobj() initializes dev->kobj and adds it below the
gendisk kobject after rnbd_clt_map_device() has returned a live
rnbd_clt_dev to rnbd_clt_map_device_store().

If kobject_init_and_add() fails, the helper currently calls
kobject_put() on the embedded kobject. That put can drop the initial
kobject reference and run rnbd_dev_release(), freeing dev. The caller
then continues through the normal error path and calls
rnbd_clt_unmap_device(dev, true, NULL), dereferencing the freed device.

Leave the initialized kobject alive until the normal device teardown has
completed and rnbd_clt_put_dev() drops the final device reference. Since
kobject_init_and_add() failure can leave the kobject initialized but not
present in sysfs, only call kobject_del() from rnbd_destroy_sysfs() when
state_in_sysfs is set.

Fixes: 581cf833cac4 ("block: rnbd: add .release to rnbd_dev_ktype")
Cc: stable@vger.kernel.org
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
---
 drivers/block/rnbd/rnbd-clt-sysfs.c | 2 +-
 drivers/block/rnbd/rnbd-clt.c       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/rnbd/rnbd-clt-sysfs.c b/drivers/block/rnbd/rnbd-clt-sysfs.c
index eb485e4c12e2..9f5d30659f3d 100644
--- a/drivers/block/rnbd/rnbd-clt-sysfs.c
+++ b/drivers/block/rnbd/rnbd-clt-sysfs.c
@@ -498,7 +498,7 @@ static int rnbd_clt_add_dev_kobj(struct rnbd_clt_dev *dev)
 	if (ret) {
 		rnbd_clt_err(dev, "Failed to create device sysfs dir, err: %d\n",
 			      ret);
-		kobject_put(&dev->kobj);
+		return ret;
 	}
 	kobject_uevent(gd_kobj, KOBJ_ONLINE);
 
diff --git a/drivers/block/rnbd/rnbd-clt.c b/drivers/block/rnbd/rnbd-clt.c
index 4d6725a0035e..5fe5c7e259b7 100644
--- a/drivers/block/rnbd/rnbd-clt.c
+++ b/drivers/block/rnbd/rnbd-clt.c
@@ -1658,7 +1658,7 @@ static void rnbd_destroy_sysfs(struct rnbd_clt_dev *dev,
 			  const struct attribute *sysfs_self)
 {
 	rnbd_clt_remove_dev_symlink(dev);
-	if (dev->kobj.state_initialized) {
+	if (dev->kobj.state_in_sysfs) {
 		if (sysfs_self)
 			/* To avoid deadlock firstly remove itself */
 			sysfs_remove_file_self(&dev->kobj, sysfs_self);
-- 
2.43.0