[PATCH] block: partition: initialize percpuref before sending out KOBJ_ADD

[PATCH] block: partition: initialize percpuref before sending out KOBJ_ADD

[Ming Lei]

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

diff --git a/block/partition-generic.c b/block/partition-generic.c
index 5d87019..84c53f0 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);
-- 
1.9.1

Re: [PATCH] block: partition: initialize percpuref before sending out KOBJ_ADD

[Christoph Hellwig]

> +	if (err) {
> +		if (flags & ADDPART_FLAG_WHOLEDISK)
> +			goto out_remove_file;
> +		goto out_del;
> +	}

I'd rather have that if around the actual device_remove_file at the
label, and jump to out_remove_file unconditionally.

Otherwise this looks fine to me.

Re: [PATCH] block: partition: initialize percpuref before sending out KOBJ_ADD

[Ming Lei]

On Thu, Mar 31, 2016 at 1:43 AM, Christoph Hellwig <hch@infradead.org> wrote:
>> +     if (err) {
>> +             if (flags & ADDPART_FLAG_WHOLEDISK)
>> +                     goto out_remove_file;
>> +             goto out_del;
>> +     }
>
> I'd rather have that if around the actual device_remove_file at the
> label, and jump to out_remove_file unconditionally.

OK, looks better.

>
> Otherwise this looks fine to me.
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