linux-kernel - [PATCH 3.2 13/46] nl80211: check netlink protocol in socket release notification

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Message-ID: <lsq.1465767281.822904363@decadent.org.uk>
Date:	Sun, 12 Jun 2016 22:34:41 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Johannes Berg" <johannes.berg@...el.com>,
	"Dmitry Ivanov" <dima@...t.com>,
	"Dmitry Ivanov" <dmitrijs.ivanovs@...t.com>
Subject: [PATCH 3.2 13/46] nl80211: check netlink protocol in socket
 release notification

3.2.81-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Ivanov <dmitrijs.ivanovs@...t.com>

commit 8f815cdde3e550e10c2736990d791f60c2ce43eb upstream.

A non-privileged user can create a netlink socket with the same port_id as
used by an existing open nl80211 netlink socket (e.g. as used by a hostapd
process) with a different protocol number.

Closing this socket will then lead to the notification going to nl80211's
socket release notification handler, and possibly cause an action such as
removing a virtual interface.

Fix this issue by checking that the netlink protocol is NETLINK_GENERIC.
Since generic netlink has no notifier chain of its own, we can't fix the
problem more generically.

Fixes: 026331c4d9b5 ("cfg80211/mac80211: allow registering for and sending action frames")
Signed-off-by: Dmitry Ivanov <dima@...t.com>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/wireless/nl80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -7496,7 +7496,7 @@ static int nl80211_netlink_notify(struct
 	struct cfg80211_registered_device *rdev;
 	struct wireless_dev *wdev;

-	if (state != NETLINK_URELEASE)
+	if (state != NETLINK_URELEASE || notify->protocol != NETLINK_GENERIC)
 		return NOTIFY_DONE;

 	rcu_read_lock();