[ 3.5.y.z extended stable ] Patch "wireless: regulatory: fix channel disabling race condition" has been added to staging queue

[Luis Henriques]

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

    wireless: regulatory: fix channel disabling race condition

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

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

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From f659fc923471b4a767e2f11b137c7a8fb8bf141b Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg at intel.com>
Date: Tue, 16 Apr 2013 14:32:26 +0200
Subject: [PATCH] wireless: regulatory: fix channel disabling race condition

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 at intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.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