[PATCH net 3/5] net: dsa: b53: clear stale state when creating an ARL entry

When an ARL lookup does not find the requested MAC and VID, b53_arl_read()
returns the first free bin index but leaves the entry populated with the
last bin examined. The multicast add path then ORs the requested port into
that unrelated entry's forwarding bitmap, potentially forwarding packets
to ports which are not members of the multicast group.

Clear the entry before creating a new one. Also return without writing
anything when deleting an entry which is not present, instead of making
a new entry from stale bin contents.

Fixes: 5d65b64a3d97 ("net: dsa: b53: Add support for MDB")
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
 drivers/net/dsa/b53/b53_common.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 559d4b360c82..0871a10d8cbc 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c

@@ -1992,6 +1992,10 @@ static int b53_arl_op(struct b53_device *dev, int op, int port,
 			addr, vid);
 		return is_valid ? ret : 0;
 	case -ENOENT:
+		if (!is_valid)
+			return 0;
+
+		memset(&ent, 0, sizeof(ent));
 		/* We could not find a matching MAC, so reset to a new entry */
 		dev_dbg(dev->dev, "{%pM,%.4d} not found, using idx: %d\n",
 			addr, vid, idx);

-- 
2.53.0