linux-kernel - [PATCH] cfg80211: Convert WARN

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Message-ID: <20240926133446.25445-1-VEfanov@ispras.ru>
Date: Thu, 26 Sep 2024 16:34:38 +0300
From: Vladislav Efanov <VEfanov@...ras.ru>
To: Johannes Berg <johannes@...solutions.net>
Cc: Vladislav Efanov <VEfanov@...ras.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org
Subject: [PATCH] cfg80211: Convert WARN_ON() to warning message

syzkaller got the following warning:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 9992 at net/wireless/ibss.c:36 __cfg80211_ibss

This warning is the result of the race condition between the following
events:

event1                          event2                      event3
__ieee80211_sta_join_ibss()        |                          |
creates new cgf80211_bss           |                          |
structure.                         |                          |
Calls cfg80211_ibss_joined()       |                          |
which will scheduled               |                          |
new event_work.                    |                          |
                         ieee80211_ibss_disconnect()          |
                         is called due to connection          |
                         dropped/ibss leaves to               |
                         remove cfg80211_bss structure.       |
                                                event_work starts.
                                          __cfg80211_ibss_joined()
                                          is called and WARNING is
                                          detected due to
                                          cfg80211_bss structure was
                                          removed by event2.

It is a normal situation when connection is dropped during handshaking.
So it looks reasonable to replace WARN_ON() with warning message to
prevent false alarm.

Found by Linux Verification Center (linuxtesting.org) with syzkaller.
Fixes: 04a773ade068 ("cfg80211/nl80211: add IBSS API")
Signed-off-by: Vladislav Efanov <VEfanov@...ras.ru>
---
 net/wireless/ibss.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/wireless/ibss.c b/net/wireless/ibss.c
index e6fdb0b8187d..93c8bee12bdf 100644
--- a/net/wireless/ibss.c
+++ b/net/wireless/ibss.c
@@ -34,8 +34,10 @@ void __cfg80211_ibss_joined(struct net_device *dev, const u8 *bssid,
 	bss = cfg80211_get_bss(wdev->wiphy, channel, bssid, NULL, 0,
 			       IEEE80211_BSS_TYPE_IBSS, IEEE80211_PRIVACY_ANY);
 
-	if (WARN_ON(!bss))
+	if (!bss) {
+		pr_warn("cfg80211: cfg80211_bss with bssid %s not found.\n", bssid);
 		return;
+	}
 
 	if (wdev->u.ibss.current_bss) {
 		cfg80211_unhold_bss(wdev->u.ibss.current_bss);
-- 
2.34.1