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>

diff --git a/net/dsa/switch.c b/net/dsa/switch.c
index 2b1b21bde830064f8a1825ff6b7c996a5219c276..8f8ed8248c2c3cd855991f706cf1426decd88d5d 100644 (file)
--- 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;
        }