linux-kernel - [PATCH 3.12 105/123] mac80211: prevent possible crypto tx tailroom corruption

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Message-Id: <1e2a5127c1407c855f13be79f650e9f84bd353ba.1438699154.git.jslaby@suse.cz>
Date:	Tue,  4 Aug 2015 16:40:49 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Michal Kazior <michal.kazior@...to.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 105/123] mac80211: prevent possible crypto tx tailroom corruption

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

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

===============

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@...to.com>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 net/mac80211/main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 2c5f21c7857f..6bf01e425911 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);
@@ -260,6 +261,8 @@ static void ieee80211_restart_work(struct work_struct *work)
 	mutex_unlock(&local->mtx);

 	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();
-- 
2.5.0

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