[PATCH 6.8 022/715] nbd: null check for nla_nest_start

[Sasha Levin]

From: Navid Emamdoost <navid.emamdoost@xxxxxxxxx>

[ Upstream commit 31edf4bbe0ba27fd03ac7d87eb2ee3d2a231af6d ]

nla_nest_start() may fail and return NULL. Insert a check and set errno
based on other call sites within the same source code.

Signed-off-by: Navid Emamdoost <navid.emamdoost@xxxxxxxxx>
Reviewed-by: Michal Kubecek <mkubecek@xxxxxxx>
Fixes: 47d902b90a32 ("nbd: add a status netlink command")
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240218042534.it.206-kees@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/block/nbd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 33a8f37bb6a1f..b7c332528ed7a 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -2433,6 +2433,12 @@ 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) {
+		nlmsg_free(reply);
+		ret = -EMSGSIZE;
+		goto out;
+	}
+
 	if (index == -1) {
 		ret = idr_for_each(&nbd_index_idr, &status_cb, reply);
 		if (ret) {
-- 
2.43.0