[PATCH v2] rbd: fix freeing memory of 'rbd_dev->opts', 'rbd_dev->spec', 'rbd_dev->rbd_client'

[Natalia Petrova]

If the rbd_dev_create() fails after assignment 'opts' to 'rbd_dev->opts',
double free of 'rbd_options' happens:
one is in rbd_dev_free() and another one is in do_rbd_add().

If the rbd_dev_create() fails, for 'spec' it will be freed in
rbd_dev_create()->rbd_spec_put() first and then in do_rbd_add()
it will call rbd_spec_put() again. The same for 'rbd_client'.
Unlike 'rbd_dev->opts', 'rbd_dev->spec' and 'rbd_dev->rbd_client'
are ref-counted, that's why the ref-count underflow warning
should be generated in rbd_spec_put() and rbd_put_client()
to handle the return values of kref_put().

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 1643dfa4c2c8 ("rbd: introduce a per-device ordered workqueue")
Signed-off-by: Natalia Petrova <n.petrova@xxxxxxxxxx>
Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
---
v2: Remarks on the processing of 'rbd_dev->spec' and 'rbd_dev->rbd_client' 
by Ilya Dryomov <idryomov@xxxxxxxxx> and Xiubo Li <xiubli@xxxxxxxxxx> 
were taken into account.
 drivers/block/rbd.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 04453f4a319c..f3f253febe0f 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -889,8 +889,10 @@ static void rbd_client_release(struct kref *kref)
  */
 static void rbd_put_client(struct rbd_client *rbdc)
 {
-	if (rbdc)
-		kref_put(&rbdc->kref, rbd_client_release);
+	if (rbdc) {
+		if (!kref_put(&rbdc->kref, rbd_client_release))
+			pr_warn("The reference count underflow\n");
+	}
 }
 
 /*
@@ -5225,8 +5227,10 @@ static struct rbd_spec *rbd_spec_get(struct rbd_spec *spec)
 static void rbd_spec_free(struct kref *kref);
 static void rbd_spec_put(struct rbd_spec *spec)
 {
-	if (spec)
-		kref_put(&spec->kref, rbd_spec_free);
+	if (spec) {
+		if (!kref_put(&spec->kref, rbd_spec_free))
+			pr_warn("The reference count underflow\n");
+	}
 }
 
 static struct rbd_spec *rbd_spec_alloc(void)
@@ -5357,7 +5361,6 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
 	if (!rbd_dev)
 		return NULL;
 
-	rbd_dev->opts = opts;
 
 	/* get an id and fill in device name */
 	rbd_dev->dev_id = ida_simple_get(&rbd_dev_id_ida, 0,
@@ -5372,6 +5375,7 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
 	if (!rbd_dev->task_wq)
 		goto fail_dev_id;
 
+	rbd_dev->opts = opts;
 	/* we have a ref from do_rbd_add() */
 	__module_get(THIS_MODULE);
 
-- 
2.34.1