[PATCH 4.5 002/200] block: partition: initialize percpuref before sending out KOBJ_ADD

[Greg Kroah-Hartman]

4.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ming Lei <ming.lei@xxxxxxxxxxxxx>

commit b30a337ca27c4f40439e4bfb290cba5f88d73bb7 upstream.

The initialization of partition's percpu_ref should have been done before
sending out KOBJ_ADD uevent, which may cause userspace to read partition
table. So the uninitialized percpu_ref may be accessed in data path.

This patch fixes this issue reported by Naveen.

Reported-by: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
Tested-by: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
Fixes: 6c71013ecb7e2(block: partition: convert percpu ref)
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 block/partition-generic.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -350,15 +350,20 @@ struct hd_struct *add_partition(struct g
 			goto out_del;
 	}
 
+	err = hd_ref_init(p);
+	if (err) {
+		if (flags & ADDPART_FLAG_WHOLEDISK)
+			goto out_remove_file;
+		goto out_del;
+	}
+
 	/* everything is up and running, commence */
 	rcu_assign_pointer(ptbl->part[partno], p);
 
 	/* suppress uevent if the disk suppresses it */
 	if (!dev_get_uevent_suppress(ddev))
 		kobject_uevent(&pdev->kobj, KOBJ_ADD);
-
-	if (!hd_ref_init(p))
-		return p;
+	return p;
 
 out_free_info:
 	free_part_info(p);
@@ -367,6 +372,8 @@ out_free_stats:
 out_free:
 	kfree(p);
 	return ERR_PTR(err);
+out_remove_file:
+	device_remove_file(pdev, &dev_attr_whole_disk);
 out_del:
 	kobject_put(p->holder_dir);
 	device_del(pdev);