netdev - [PATCH net-next 4/6 v5] net: dsa: rtl8366rb: Fix off-by-one bug

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Date:   Sat, 25 Sep 2021 01:36:26 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>,
        Mauri Sandberg <sandberg@...lfence.com>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        DENG Qingfang <dqfext@...il.com>
Subject: [PATCH net-next 4/6 v5] net: dsa: rtl8366rb: Fix off-by-one bug

The max VLAN number with non-4K VLAN activated is 15, and the
range is 0..15. Not 16.

The impact should be low since we by default have 4K VLAN and
thus have 4095 VLANs to play with in this switch. There will
not be a problem unless the code is rewritten to only use
16 VLANs.

Fixes: d8652956cf37 ("net: dsa: realtek-smi: Add Realtek SMI driver")
Cc: Vladimir Oltean <olteanv@...il.com>
Cc: Mauri Sandberg <sandberg@...lfence.com>
Cc: Alvin Šipraga <alsi@...g-olufsen.dk>
Cc: DENG Qingfang <dqfext@...il.com>
Cc: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
---
ChangeLog v4->v5:
- Add some more text describing that this is not a critical bug.
- Add Fixes tag
ChangeLog v1->v4:
- New patch for a bug discovered when fixing the other issues.
---
 drivers/net/dsa/rtl8366rb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/dsa/rtl8366rb.c b/drivers/net/dsa/rtl8366rb.c
index 1f228a7a5685..7e57442ab0ca 100644
--- a/drivers/net/dsa/rtl8366rb.c
+++ b/drivers/net/dsa/rtl8366rb.c
@@ -1451,7 +1451,7 @@ static int rtl8366rb_set_mc_index(struct realtek_smi *smi, int port, int index)
 
 static bool rtl8366rb_is_vlan_valid(struct realtek_smi *smi, unsigned int vlan)
 {
-	unsigned int max = RTL8366RB_NUM_VLANS;
+	unsigned int max = RTL8366RB_NUM_VLANS - 1;
 
 	if (smi->vlan4k_enabled)
 		max = RTL8366RB_NUM_VIDS - 1;
-- 
2.31.1