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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Johannes Berg <johannes.berg@intel.com>
Subject: [PATCH 5.4 20/51] cfg80211: scan: fix RCU in cfg80211_add_nontrans_list()
Date:   Mon,  1 Nov 2021 10:17:24 +0100
Message-Id: <20211101082505.200852489@linuxfoundation.org>
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References: <20211101082500.203657870@linuxfoundation.org>
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From: Johannes Berg <johannes.berg@intel.com>

commit a2083eeb119fb9307258baea9b7c243ca9a2e0b6 upstream.

The SSID pointer is pointing to RCU protected data, so we
need to have it under rcu_read_lock() for the entire use.
Fix this.

Cc: stable@vger.kernel.org
Fixes: 0b8fb8235be8 ("cfg80211: Parsing of Multiple BSSID information in scanning")
Link: https://lore.kernel.org/r/20210930131120.6ddfc603aa1d.I2137344c4e2426525b1a8e4ce5fca82f8ecbfe7e@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/wireless/scan.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -379,14 +379,17 @@ cfg80211_add_nontrans_list(struct cfg802
 	}
 	ssid_len = ssid[1];
 	ssid = ssid + 2;
-	rcu_read_unlock();
 
 	/* check if nontrans_bss is in the list */
 	list_for_each_entry(bss, &trans_bss->nontrans_list, nontrans_list) {
-		if (is_bss(bss, nontrans_bss->bssid, ssid, ssid_len))
+		if (is_bss(bss, nontrans_bss->bssid, ssid, ssid_len)) {
+			rcu_read_unlock();
 			return 0;
+		}
 	}
 
+	rcu_read_unlock();
+
 	/* add to the list */
 	list_add_tail(&nontrans_bss->nontrans_list, &trans_bss->nontrans_list);
 	return 0;