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Commit 1f2c6651 authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

rbd: don't leak parent_spec in rbd_dev_probe_parent() 



Currently we leak parent_spec and trigger a "parent reference
underflow" warning if rbd_dev_create() in rbd_dev_probe_parent() fails.
The problem is we take the !parent out_err branch and that only drops
refcounts; parent_spec that would've been freed had we called
rbd_dev_unparent() remains and triggers rbd_warn() in
rbd_dev_parent_put() - at that point we have parent_spec != NULL and
parent_ref == 0, so counter ends up being -1 after the decrement.

Redo rbd_dev_probe_parent() to fix this.

Cc: stable@vger.kernel.org # 3.10+, needs backporting for < 4.2
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
Reviewed-by: default avatarAlex Elder <elder@linaro.org>
parent 7379047d

drivers/block/rbd.c

+16 −20
Original line number Original line Diff line number Diff line
@@ -5134,41 +5134,37 @@ static int rbd_dev_v2_header_onetime(struct rbd_device *rbd_dev) 
static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)

static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)

{

{

	struct rbd_device *parent = NULL;

	struct rbd_device *parent = NULL;

	struct rbd_spec *parent_spec;

	struct rbd_client *rbdc;

	int ret;

	int ret;





	if (!rbd_dev->parent_spec)

	if (!rbd_dev->parent_spec)

		return 0;

		return 0;

	/*

	 * We need to pass a reference to the client and the parent

	 * spec when creating the parent rbd_dev.  Images related by

	 * parent/child relationships always share both.

	 */

	parent_spec = rbd_spec_get(rbd_dev->parent_spec);

	rbdc = __rbd_get_client(rbd_dev->rbd_client);





	parent = rbd_dev_create(rbd_dev->rbd_client, rbd_dev->parent_spec,

				NULL);

	if (!parent) {

		ret = -ENOMEM;

		ret = -ENOMEM;

	parent = rbd_dev_create(rbdc, parent_spec, NULL);

	if (!parent)

		goto out_err;

		goto out_err;

	}



	/*

	 * Images related by parent/child relationships always share

	 * rbd_client and spec/parent_spec, so bump their refcounts.

	 */

	__rbd_get_client(rbd_dev->rbd_client);

	rbd_spec_get(rbd_dev->parent_spec);





	ret = rbd_dev_image_probe(parent, false);

	ret = rbd_dev_image_probe(parent, false);

	if (ret < 0)

	if (ret < 0)

		goto out_err;

		goto out_err;



	rbd_dev->parent = parent;

	rbd_dev->parent = parent;

	atomic_set(&rbd_dev->parent_ref, 1);

	atomic_set(&rbd_dev->parent_ref, 1);



	return 0;

	return 0;



out_err:

out_err:

	if (parent) {

	rbd_dev_unparent(rbd_dev);

	rbd_dev_unparent(rbd_dev);

	if (parent)

		rbd_dev_destroy(parent);

		rbd_dev_destroy(parent);

	} else {

		rbd_put_client(rbdc);

		rbd_spec_put(parent_spec);

	}



	return ret;

	return ret;

}

}