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

From: Willy Tarreau
Date: Sun Jun 05 2016 - 06:22:52 EST

From: Dmitry Ivanov <dmitrijs.ivanovs@xxxxxxxx>

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@xxxxxxxxxxxxxxx
Signed-off-by: Dmitry Ivanov <dima@xxxxxxxx>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
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)