[PATCH v4] nbd: null check for nla_nest_start

From: Kees Cook <keescook@chromium.org>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Kees Cook <keescook@chromium.org>,
	Navid Emamdoost <navid.emamdoost@gmail.com>,
	Michal Kubecek <mkubecek@suse.cz>, Jens Axboe <axboe@kernel.dk>,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	nbd@other.debian.org, linux-hardening@vger.kernel.org
Subject: [PATCH v4] nbd: null check for nla_nest_start
Date: Sat, 17 Feb 2024 20:25:38 -0800	[thread overview]
Message-ID: <20240218042534.it.206-kees@kernel.org> (raw)

From: Navid Emamdoost <navid.emamdoost@gmail.com>

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@gmail.com>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Fixes: 47d902b90a32 ("nbd: add a status netlink command")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v3- https://lore.kernel.org/lkml/20190911164013.27364-1-navid.emamdoost@gmail.com/
Resending on behalf of the author. This seems to have gotten lost and
has been getting tracked as CVE-2019-16089 ever since. For example:
https://ubuntu.com/security/CVE-2019-16089
---
 drivers/block/nbd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 33a8f37bb6a1..b7c332528ed7 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) {
-- 
2.34.1

