linux-kernel - [PATCH] net: openvswitch: silence suspicious RCU usage warning

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Message-Id: <20200805071911.64101-1-xiangxia.m.yue@gmail.com>
Date:   Wed,  5 Aug 2020 15:19:11 +0800
From:   xiangxia.m.yue@...il.com
To:     davem@...emloft.net, echaudro@...hat.com, kuba@...nel.org,
        pabeni@...hat.com, pshelar@....org, syzkaller-bugs@...glegroups.com
Cc:     dev@...nvswitch.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, Tonghao Zhang <xiangxia.m.yue@...il.com>
Subject: [PATCH] net: openvswitch: silence suspicious RCU usage warning

From: Tonghao Zhang <xiangxia.m.yue@...il.com>

ovs_flow_tbl_destroy always is called from RCU callback
or error path. It is no need to check if rcu_read_lock
or lockdep_ovsl_is_held was held.

ovs_dp_cmd_fill_info always is called with ovs_mutex,
So use the rcu_dereference_ovsl instead of rcu_dereference
in ovs_flow_tbl_masks_cache_size.

Fixes: 9bf24f594c6a ("net: openvswitch: make masks cache size configurable")
Cc: Eelco Chaudron <echaudro@...hat.com>
Reported-by: syzbot+c0eb9e7cdde04e4eb4be@...kaller.appspotmail.com
Reported-by: syzbot+f612c02823acb02ff9bc@...kaller.appspotmail.com
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
---
 net/openvswitch/flow_table.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index 6527d84c3ea6..8c12675cbb67 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -518,8 +518,8 @@ void ovs_flow_tbl_destroy(struct flow_table *table)
 {
 	struct table_instance *ti = rcu_dereference_raw(table->ti);
 	struct table_instance *ufid_ti = rcu_dereference_raw(table->ufid_ti);
-	struct mask_cache *mc = rcu_dereference(table->mask_cache);
-	struct mask_array *ma = rcu_dereference_ovsl(table->mask_array);
+	struct mask_cache *mc = rcu_dereference_raw(table->mask_cache);
+	struct mask_array *ma = rcu_dereference_raw(table->mask_array);
 
 	call_rcu(&mc->rcu, mask_cache_rcu_cb);
 	call_rcu(&ma->rcu, mask_array_rcu_cb);
@@ -937,7 +937,7 @@ int ovs_flow_tbl_num_masks(const struct flow_table *table)
 
 u32 ovs_flow_tbl_masks_cache_size(const struct flow_table *table)
 {
-	struct mask_cache *mc = rcu_dereference(table->mask_cache);
+	struct mask_cache *mc = rcu_dereference_ovsl(table->mask_cache);
 
 	return READ_ONCE(mc->cache_size);
 }
-- 
2.26.1