linux-kernel - [PATCH net] drivers: net: hamradio: Fix suspicious RCU usage warning in bpqether.c

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Date:   Thu, 14 May 2020 19:41:15 +0530
From:   madhuparnabhowmik10@...il.com
To:     davem@...emloft.net, allison@...utok.net, tglx@...utronix.de,
        ap420073@...il.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org, paulmck@...nel.org,
        cai@....pw, joel@...lfernandes.org, frextrite@...il.com,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Subject: [PATCH net] drivers: net: hamradio: Fix suspicious RCU usage warning in bpqether.c

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

This patch fixes the following warning:
=============================
WARNING: suspicious RCU usage
5.7.0-rc5-next-20200514-syzkaller #0 Not tainted
-----------------------------
drivers/net/hamradio/bpqether.c:149 RCU-list traversed in non-reader section!!

Since rtnl lock is held, pass this cond in list_for_each_entry_rcu().

Reported-by: syzbot+bb82cafc737c002d11ca@...kaller.appspotmail.com
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 drivers/net/hamradio/bpqether.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/hamradio/bpqether.c b/drivers/net/hamradio/bpqether.c
index fbea6f232819..e2ad3c2e8df5 100644
--- a/drivers/net/hamradio/bpqether.c
+++ b/drivers/net/hamradio/bpqether.c
@@ -127,7 +127,8 @@ static inline struct net_device *bpq_get_ax25_dev(struct net_device *dev)
 {
 	struct bpqdev *bpq;
 
-	list_for_each_entry_rcu(bpq, &bpq_devices, bpq_list) {
+	list_for_each_entry_rcu(bpq, &bpq_devices, bpq_list,
+				lockdep_rtnl_is_held()) {
 		if (bpq->ethdev == dev)
 			return bpq->axdev;
 	}
-- 
2.17.1