linux-kernel - [PATCH 1/2] cfg80211: fix dead lock for nl80211_new

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Message-Id: <20220921091913.110749-1-arda@allwinnertech.com>
Date:   Wed, 21 Sep 2022 17:19:12 +0800
From:   Aran Dalton <arda@...winnertech.com>
To:     johannes@...solutions.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Cc:     johannes.berg@...el.com, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] cfg80211: fix dead lock for nl80211_new_interface()

Both nl80211_new_interface and cfg80211_netdev_notifier_call hold the
same wiphy_lock, then cause deadlock.

The main call stack as bellow:

nl80211_new_interface() takes wiphy_lock
 -> _nl80211_new_interface:
  -> rdev_add_virtual_intf
   -> rdev->ops->add_virtual_intf
    -> register_netdevice
     -> call_netdevice_notifiers(NETDEV_REGISTER, dev);
      -> call_netdevice_notifiers_extack
       -> call_netdevice_notifiers_info
        -> raw_notifier_call_chain
         -> cfg80211_netdev_notifier_call
          -> wiphy_lock(&rdev->wiphy), cfg80211_register_wdev

Fixes: ea6b2098dd02 ("cfg80211: fix locking in netlink owner interface destruction")
Signed-off-by: Aran Dalton <arda@...winnertech.com>
---
 net/wireless/nl80211.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 2705e3ee8fc4..bdacddc3ffa3 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -4260,9 +4260,7 @@ static int nl80211_new_interface(struct sk_buff *skb, struct genl_info *info)
 	/* to avoid failing a new interface creation due to pending removal */
 	cfg80211_destroy_ifaces(rdev);
 
-	wiphy_lock(&rdev->wiphy);
 	ret = _nl80211_new_interface(skb, info);
-	wiphy_unlock(&rdev->wiphy);
 
 	return ret;
 }
-- 
2.29.0