[3.16.y-ckt stable] Patch "mac80211: prevent possible crypto tx tailroom corruption" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    mac80211: prevent possible crypto tx tailroom corruption

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt15.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From b9132b089d13ebbb5e067d5645761274e3a5cd63 Mon Sep 17 00:00:00 2001
From: Michal Kazior <michal.kazior at tieto.com>
Date: Fri, 22 May 2015 10:22:40 +0200
Subject: mac80211: prevent possible crypto tx tailroom corruption

commit ab499db80fcf07c18e4053f91a619500f663e90e upstream.

There was a possible race between
ieee80211_reconfig() and
ieee80211_delayed_tailroom_dec(). This could
result in inability to transmit data if driver
crashed during roaming or rekeying and subsequent
skbs with insufficient tailroom appeared.

This race was probably never seen in the wild
because a device driver would have to crash AND
recover within 0.5s which is very unlikely.

I was able to prove this race exists after
changing the delay to 10s locally and crashing
ath10k via debugfs immediately after GTK
rekeying. In case of ath10k the counter went below
0. This was harmless but other drivers which
actually require tailroom (e.g. for WEP ICV or
MMIC) could end up with the counter at 0 instead
of >0 and introduce insufficient skb tailroom
failures because mac80211 would not resize skbs
appropriately anymore.

Fixes: 8d1f7ecd2af5 ("mac80211: defer tailroom counter manipulation when roaming")
Signed-off-by: Michal Kazior <michal.kazior at tieto.com>
Signed-off-by: Johannes Berg <johannes.berg at intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/mac80211/main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index d17c26d6e369..8915b1e081e4 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -248,6 +248,7 @@ static void ieee80211_restart_work(struct work_struct *work)
 {
 	struct ieee80211_local *local =
 		container_of(work, struct ieee80211_local, restart_work);
+	struct ieee80211_sub_if_data *sdata;

 	/* wait for scan work complete */
 	flush_workqueue(local->workqueue);
@@ -256,6 +257,8 @@ static void ieee80211_restart_work(struct work_struct *work)
 	     "%s called with hardware scan in progress\n", __func__);

 	rtnl_lock();
+	list_for_each_entry(sdata, &local->interfaces, list)
+		flush_delayed_work(&sdata->dec_tailroom_needed_wk);
 	ieee80211_scan_cancel(local);
 	ieee80211_reconfig(local);
 	rtnl_unlock();