From 232deb3f9567ce37d99b8616a6c07c1fc0436abf Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: Sun, 24 Oct 2021 20:17:48 +0300
Subject: [PATCH] net: dsa: avoid refcount warnings when ->port_{fdb,mdb}_del
 returns error

At present, when either of ds->ops->port_fdb_del() or ds->ops->port_mdb_del()
return a non-zero error code, we attempt to save the day and keep the
data structure associated with that switchdev object, as the deletion
procedure did not complete.

However, the way in which we do this is suspicious to the checker in
lib/refcount.c, who thinks it is buggy to increment a refcount that
became zero, and that this is indicative of a use-after-free.

Fixes: 161ca59d39e9 ("net: dsa: reference count the MDB entries at the cross-chip notifier level")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/dsa/switch.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/dsa/switch.c b/net/dsa/switch.c
index 2b1b21bde8300..8f8ed8248c2c3 100644
--- a/net/dsa/switch.c
+++ b/net/dsa/switch.c
@@ -266,7 +266,7 @@ static int dsa_port_do_mdb_del(struct dsa_port *dp,
 
 	err = ds->ops->port_mdb_del(ds, port, mdb);
 	if (err) {
-		refcount_inc(&a->refcount);
+		refcount_set(&a->refcount, 1);
 		return err;
 	}
 
@@ -333,7 +333,7 @@ static int dsa_port_do_fdb_del(struct dsa_port *dp, const unsigned char *addr,
 
 	err = ds->ops->port_fdb_del(ds, port, addr, vid);
 	if (err) {
-		refcount_inc(&a->refcount);
+		refcount_set(&a->refcount, 1);
 		return err;
 	}