block: partition: initialize percpuref before sending out KOBJ_ADD

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@codeaurora.org>
Tested-by: Naveen Kaje <nkaje@codeaurora.org>
Fixes: 6c71013ecb7e2(block: partition: convert percpu ref)
Cc: <stable@vger.kernel.org> # v4.3+
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/block/partition-generic.c b/block/partition-generic.c
index 5d8701941054..84c53f04777a 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -361,15 +361,20 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
                         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);
@@ -378,6 +383,8 @@ 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);