linux-kernel - [PATCH 089/118] wireless: regulatory: fix channel disabling race condition

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Message-Id: <1367933964-1564-90-git-send-email-luis.henriques@canonical.com>
Date:	Tue,  7 May 2013 14:38:55 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Johannes Berg <johannes.berg@...el.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 089/118] wireless: regulatory: fix channel disabling race condition

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

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

From: Johannes Berg <johannes.berg@...el.com>

commit 990de49f74e772b6db5208457b7aa712a5f4db86 upstream.

When a full scan 2.4 and 5 GHz scan is scheduled, but then the 2.4 GHz
part of the scan disables a 5.2 GHz channel due to, e.g. receiving
country or frequency information, that 5.2 GHz channel might already
be in the list of channels to scan next. Then, when the driver checks
if it should do a passive scan, that will return false and attempt an
active scan. This is not only wrong but can also lead to the iwlwifi
device firmware crashing since it checks regulatory as well.

Fix this by not setting the channel flags to just disabled but rather
OR'ing in the disabled flag. That way, even if the race happens, the
channel will be scanned passively which is still (mostly) correct.

Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 net/wireless/reg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index 4dc8347..796a0ee 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -862,7 +862,7 @@ static void handle_channel(struct wiphy *wiphy,
 			return;

 		REG_DBG_PRINT("Disabling freq %d MHz\n", chan->center_freq);
-		chan->flags = IEEE80211_CHAN_DISABLED;
+		chan->flags |= IEEE80211_CHAN_DISABLED;
 		return;
 	}

-- 
1.8.1.2

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