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rbd: don't leak parent_spec in rbd_dev_probe_parent()

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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: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
This commit is contained in:
Ilya Dryomov 2015-10-11 19:38:00 +02:00
parent 7379047d55
commit 1f2c6651f6
1 changed files with 17 additions and 21 deletions
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38
drivers/block/rbd.c
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@ -5134,41 +5134,37 @@ out_err:
static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
{
struct rbd_device *parent = NULL;
struct rbd_spec *parent_spec;
struct rbd_client *rbdc;
int ret;
if (!rbd_dev->parent_spec)
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);
ret = -ENOMEM;
parent = rbd_dev_create(rbdc, parent_spec, NULL);
if (!parent)
parent = rbd_dev_create(rbd_dev->rbd_client, rbd_dev->parent_spec,
NULL);
if (!parent) {
ret = -ENOMEM;
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);
if (ret < 0)
goto out_err;
rbd_dev->parent = parent;
atomic_set(&rbd_dev->parent_ref, 1);
return 0;
out_err:
if (parent) {
rbd_dev_unparent(rbd_dev);
rbd_dev_destroy(parent);
} else {
rbd_put_client(rbdc);
rbd_spec_put(parent_spec);
}
out_err:
rbd_dev_unparent(rbd_dev);
if (parent)
rbd_dev_destroy(parent);
return ret;
}