linux-kernel - [PATCH 3.10 086/143] nl80211: check netlink protocol in socket release notification

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Message-Id: <1465122046-9645-87-git-send-email-w@1wt.eu>
Date:	Sun,  5 Jun 2016 12:19:49 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Dmitry Ivanov <dmitrijs.ivanovs@...t.com>,
	Dmitry Ivanov <dima@...t.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 086/143] nl80211: check netlink protocol in socket release notification

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")
Cc: stable@...r.kernel.org
Signed-off-by: Dmitry Ivanov <dima@...t.com>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 net/wireless/nl80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 90a0e55..dd3dbed 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -10685,7 +10685,7 @@ static int nl80211_netlink_notify(struct notifier_block * nb,
 	struct wireless_dev *wdev;
 	struct cfg80211_beacon_registration *reg, *tmp;
 
-	if (state != NETLINK_URELEASE)
+	if (state != NETLINK_URELEASE || notify->protocol != NETLINK_GENERIC)
 		return NOTIFY_DONE;
 
 	rcu_read_lock();
-- 
2.8.0.rc2.1.gbe9624a