[PATCH] nbd_genl_status: null check for nla_nest_start

[Navid Emamdoost <navid.emamdoost@xxxxxxxxx>]

nla_nest_start may fail and return NULL. The check is inserted, and
errno is selected based on other call sites within the same source code.

Signed-off-by: Navid Emamdoost <navid.emamdoost@xxxxxxxxx>
---
 drivers/block/nbd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 9bcde2325893..dba362de4d91 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -2149,6 +2149,12 @@ static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	dev_list = nla_nest_start_noflag(reply, NBD_ATTR_DEVICE_LIST);
+
+	if (!dev_list) {
+		ret = -EMSGSIZE;
+		goto out;
+	}
+
 	if (index == -1) {
 		ret = idr_for_each(&nbd_index_idr, &status_cb, reply);
 		if (ret) {
-- 
2.17.1