netdev - [PATCH net-next 4/6 v7] net: dsa: rtl8366rb: Fix off-by-one bug

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Date:   Sun, 26 Sep 2021 00:59:27 +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>,
        DENG Qingfang <dqfext@...il.com>,
        Alvin Šipraga <alsi@...g-olufsen.dk>
Subject: [PATCH net-next 4/6 v7] 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: Mauri Sandberg <sandberg@...lfence.com>
Cc: DENG Qingfang <dqfext@...il.com>
Cc: Florian Fainelli <f.fainelli@...il.com>
Reviewed-by: Alvin Šipraga <alsi@...g-olufsen.dk>
Reviewed-by: Vladimir Oltean <olteanv@...il.com>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
---
ChangeLog v6->v7:
- Collect Alvin's and Vladimir's review tags.
ChangeLog v5->v6:
- No changes just resending with the rest of the
  patches.
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 01d794f94156..6382404814c3 100644
--- a/drivers/net/dsa/rtl8366rb.c
+++ b/drivers/net/dsa/rtl8366rb.c
@@ -1520,7 +1520,7 @@ 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