nl80211: check netlink protocol in socket release notification

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@ubnt.com>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index e1f73b6..446d224 100644 (file)
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -7496,7 +7496,7 @@ static int nl80211_netlink_notify(struct notifier_block * nb,
        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();