linux-kernel - [PATCH v1] block: partition: initialize percpuref before new partition is visiable

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Date:	Thu, 31 Mar 2016 10:40:27 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org
Cc:	linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
	Naveen Kaje <nkaje@...eaurora.org>,
	Ming Lei <ming.lei@...onical.com>, <stable@...r.kernel.org>
Subject: [PATCH v1] block: partition: initialize percpuref before new partition is visiable

The initialization of partition's percpu_ref should have been done before
the new partition is updated to partition table via
rcu_assign_pointer(), otherwise the uninitialized percpu_ref may be accessed
in data path.

This patch fixes this issue reported by Naveen.

Reported-by: Naveen Kaje <nkaje@...eaurora.org>
Tested-by: Naveen Kaje <nkaje@...eaurora.org>
Fixes: 6c71013ecb7e2(block: partition: convert percpu ref)
Cc: <stable@...r.kernel.org> # v4.3+
Signed-off-by: Ming Lei <ming.lei@...onical.com>
---
V1:
	- put 'if' around the actual device_remove_file at the label
	as suggested by Christoph
	- make commit log more accurate

 block/partition-generic.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/block/partition-generic.c b/block/partition-generic.c
index 5d87019..54d4be8 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -361,15 +361,17 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
 			goto out_del;
 	}
 
+	err = hd_ref_init(p);
+	if (err)
+		goto out_remove_file;
+
 	/* 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 +380,9 @@ out_free_stats:
 out_free:
 	kfree(p);
 	return ERR_PTR(err);
+out_remove_file:
+	if (flags & ADDPART_FLAG_WHOLEDISK)
+		device_remove_file(pdev, &dev_attr_whole_disk);
 out_del:
 	kobject_put(p->holder_dir);
 	device_del(pdev);
-- 
1.9.1