netdev - [PATCH net] mac80211: fix locking in ieee80211_start

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Message-Id: <20211220092240.12768-1-johannes@sipsolutions.net>
Date:   Mon, 20 Dec 2021 10:22:40 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     Johannes Berg <johannes.berg@...el.com>, stable@...r.kernel.org,
        syzbot+11c342e5e30e9539cabd@...kaller.appspotmail.com
Subject: [PATCH net] mac80211: fix locking in ieee80211_start_ap error path

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

We need to hold the local->mtx to release the channel context,
as even encoded by the lockdep_assert_held() there. Fix it.

Cc: stable@...r.kernel.org
Fixes: 295b02c4be74 ("mac80211: Add FILS discovery support")
Reported-and-tested-by: syzbot+11c342e5e30e9539cabd@...kaller.appspotmail.com
Link: https://lore.kernel.org/r/20211220090836.cee3d59a1915.I36bba9b79dc2ff4d57c3c7aa30dff9a003fe8c5c@changeid
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
Jakub/Dave, could you please apply this directly? I have no
other things pending for net at the moment. Thanks!
---
 net/mac80211/cfg.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index bd3d3195097f..2d0dd69f9753 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1264,7 +1264,10 @@ static int ieee80211_start_ap(struct wiphy *wiphy, struct net_device *dev,
 	return 0;
 
 error:
+	mutex_lock(&local->mtx);
 	ieee80211_vif_release_channel(sdata);
+	mutex_unlock(&local->mtx);
+
 	return err;
 }
 
-- 
2.33.1