netdev - [PATCH net] net: openvswitch: fix nested key length validation in the set() action

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Message-ID: <20250412104052.2073688-1-i.maximets@ovn.org>
Date: Sat, 12 Apr 2025 12:40:18 +0200
From: Ilya Maximets <i.maximets@....org>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	dev@...nvswitch.org,
	linux-kernel@...r.kernel.org,
	Eelco Chaudron <echaudro@...hat.com>,
	Aaron Conole <aconole@...hat.com>,
	Ilya Maximets <i.maximets@....org>,
	syzbot+b07a9da40df1576b8048@...kaller.appspotmail.com
Subject: [PATCH net] net: openvswitch: fix nested key length validation in the set() action

It's not safe to access nla_len(ovs_key) if the data is smaller than
the netlink header.  Check that the attribute is OK first.

Fixes: ccb1352e76cf ("net: Add Open vSwitch kernel components.")
Reported-by: syzbot+b07a9da40df1576b8048@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b07a9da40df1576b8048
Tested-by: syzbot+b07a9da40df1576b8048@...kaller.appspotmail.com
Signed-off-by: Ilya Maximets <i.maximets@....org>
---
 net/openvswitch/flow_netlink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 95e0dd14dc1a..518be23e48ea 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -2876,7 +2876,8 @@ static int validate_set(const struct nlattr *a,
 	size_t key_len;
 
 	/* There can be only one key in a action */
-	if (nla_total_size(nla_len(ovs_key)) != nla_len(a))
+	if (!nla_ok(ovs_key, nla_len(a)) ||
+	    nla_total_size(nla_len(ovs_key)) != nla_len(a))
 		return -EINVAL;
 
 	key_len = nla_len(ovs_key);
-- 
2.49.0