2020-02-22 16:59:01

by Amol Grover

Subject: [PATCH] ip6mr: Fix RCU list debugging warning

ip6mr_for_each_table() macro uses list_for_each_entry_rcu()
for traversing outside an RCU read side critical section
but under the protection of rtnl_mutex. Hence add the
corresponding lockdep expression to silence the following
false-positive warnings:

[ 4.319479] =============================
[ 4.319480] WARNING: suspicious RCU usage
[ 4.319482] 5.5.4-stable #17 Tainted: G E
[ 4.319483] -----------------------------
[ 4.319485] net/ipv6/ip6mr.c:1243 RCU-list traversed in non-reader section!!

[ 4.456831] =============================
[ 4.456832] WARNING: suspicious RCU usage
[ 4.456834] 5.5.4-stable #17 Tainted: G E
[ 4.456835] -----------------------------
[ 4.456837] net/ipv6/ip6mr.c:1582 RCU-list traversed in non-reader section!!

Signed-off-by: Amol Grover <[email protected]>
---
net/ipv6/ip6mr.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index bfa49ff70531..d6483926f449 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -97,7 +97,8 @@ static void ipmr_expire_process(struct timer_list *t);

#ifdef CONFIG_IPV6_MROUTE_MULTIPLE_TABLES
#define ip6mr_for_each_table(mrt, net) \
- list_for_each_entry_rcu(mrt, &net->ipv6.mr6_tables, list)
+ list_for_each_entry_rcu(mrt, &net->ipv6.mr6_tables, list, \
+ lockdep_rtnl_is_held())

static struct mr_table *ip6mr_mr_table_iter(struct net *net,
struct mr_table *mrt)
--
2.24.1

2020-02-24 21:20:25

by David Miller

Subject: Re: [PATCH] ip6mr: Fix RCU list debugging warning

From: Amol Grover <[email protected]>
Date: Sat, 22 Feb 2020 22:27:27 +0530

> ip6mr_for_each_table() macro uses list_for_each_entry_rcu()
> for traversing outside an RCU read side critical section
> but under the protection of rtnl_mutex. Hence add the
> corresponding lockdep expression to silence the following
> false-positive warnings:
>
> [ 4.319479] =============================
> [ 4.319480] WARNING: suspicious RCU usage
> [ 4.319482] 5.5.4-stable #17 Tainted: G E
> [ 4.319483] -----------------------------
> [ 4.319485] net/ipv6/ip6mr.c:1243 RCU-list traversed in non-reader section!!
>
> [ 4.456831] =============================
> [ 4.456832] WARNING: suspicious RCU usage
> [ 4.456834] 5.5.4-stable #17 Tainted: G E
> [ 4.456835] -----------------------------
> [ 4.456837] net/ipv6/ip6mr.c:1582 RCU-list traversed in non-reader section!!
>
> Signed-off-by: Amol Grover <[email protected]>

Applied, thanks.