linux-kernel - [PATCH 4.1 227/267] cfg80211: ignore netif running state when changing iftype

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Message-Id: <20150731194010.399818794@linuxfoundation.org>
Date:	Fri, 31 Jul 2015 12:41:18 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Michal Kazior <michal.kazior@...to.com>,
	Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 4.1 227/267] cfg80211: ignore netif running state when changing iftype

4.1-stable review patch.  If anyone has any objections, please let me know.

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

From: Michal Kazior <michal.kazior@...to.com>

commit 6cbfb1bb66e4e85da5db78e8ff429a85bd84ce64 upstream.

It was possible for mac80211 to be coerced into an
unexpected flow causing sdata union to become
corrupted. Station pointer was put into
sdata->u.vlan.sta memory location while it was
really master AP's sdata->u.ap.next_beacon. This
led to station entry being later freed as
next_beacon before __sta_info_flush() in
ieee80211_stop_ap() and a subsequent invalid
pointer dereference crash.

The problem was that ieee80211_ptr->use_4addr
wasn't cleared on interface type changes.

This could be reproduced with the following steps:

 # host A and host B have just booted; no
 # wpa_s/hostapd running; all vifs are down
 host A> iw wlan0 set type station
 host A> iw wlan0 set 4addr on
 host A> printf 'interface=wlan0\nssid=4addrcrash\nchannel=1\nwds_sta=1' > /tmp/hconf
 host A> hostapd -B /tmp/conf
 host B> iw wlan0 set 4addr on
 host B> ifconfig wlan0 up
 host B> iw wlan0 connect -w hostAssid
 host A> pkill hostapd
 # host A crashed:

 [  127.928192] BUG: unable to handle kernel NULL pointer dereference at 00000000000006c8
 [  127.929014] IP: [<ffffffff816f4f32>] __sta_info_flush+0xac/0x158
 ...
 [  127.934578]  [<ffffffff8170789e>] ieee80211_stop_ap+0x139/0x26c
 [  127.934578]  [<ffffffff8100498f>] ? dump_trace+0x279/0x28a
 [  127.934578]  [<ffffffff816dc661>] __cfg80211_stop_ap+0x84/0x191
 [  127.934578]  [<ffffffff816dc7ad>] cfg80211_stop_ap+0x3f/0x58
 [  127.934578]  [<ffffffff816c5ad6>] nl80211_stop_ap+0x1b/0x1d
 [  127.934578]  [<ffffffff815e53f8>] genl_family_rcv_msg+0x259/0x2b5

Note: This isn't a revert of f8cdddb8d61d
("cfg80211: check iface combinations only when
iface is running") as far as functionality is
considered because b6a550156bc ("cfg80211/mac80211:
move more combination checks to mac80211") moved
the logic somewhere else already.

Fixes: f8cdddb8d61d ("cfg80211: check iface combinations only when iface is running")
Signed-off-by: Michal Kazior <michal.kazior@...to.com>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/wireless/util.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -944,7 +944,7 @@ int cfg80211_change_iface(struct cfg8021
 	     ntype == NL80211_IFTYPE_P2P_CLIENT))
 		return -EBUSY;
 
-	if (ntype != otype && netif_running(dev)) {
+	if (ntype != otype) {
 		dev->ieee80211_ptr->use_4addr = false;
 		dev->ieee80211_ptr->mesh_id_up_len = 0;
 		wdev_lock(dev->ieee80211_ptr);


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