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

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

[madhuparnabhowmik10]

From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.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@syzkaller.appspotmail.com
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.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

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

[David Miller]

From: madhuparnabhowmik10@gmail.com
Date: Thu, 14 May 2020 19:41:15 +0530

> From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.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@syzkaller.appspotmail.com
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>

Applied, thanks.
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