netdev - [PATCH net-next] net: dsa: Fix off by one in dsa_loop_port_vlan

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Date:   Tue, 19 Jan 2021 17:53:35 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     "; Andrew Lunn" <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH net-next] net: dsa: Fix off by one in dsa_loop_port_vlan_add()

The > comparison is intended to be >= to prevent reading beyond the
end of the ps->vlans[] array.  It doesn't affect run time though because
the ps->vlans[] array has VLAN_N_VID (4096) elements and the vlan->vid
cannot be > 4094 because it is checked earlier.

Fixes: 98cd1552ea27 ("net: dsa: Mock-up driver")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
I'm not 100% sure where this is checked but the other code has comments
and assumptions that say that it is and Smatch says that it is.  If I
had to guess, I would say that the check is in the nla policy.

[NL80211_ATTR_VLAN_ID] = NLA_POLICY_RANGE(NLA_U16, 1, VLAN_N_VID - 2),

This patch is against linux-next.  I could re-write it against net if
you want.  Another option would be to just delete the sanity check.

 drivers/net/dsa/dsa_loop.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/dsa/dsa_loop.c b/drivers/net/dsa/dsa_loop.c
index 5f69216376fe..8c283f59158b 100644
--- a/drivers/net/dsa/dsa_loop.c
+++ b/drivers/net/dsa/dsa_loop.c
@@ -207,7 +207,7 @@ static int dsa_loop_port_vlan_add(struct dsa_switch *ds, int port,
 	struct mii_bus *bus = ps->bus;
 	struct dsa_loop_vlan *vl;
 
-	if (vlan->vid > ARRAY_SIZE(ps->vlans))
+	if (vlan->vid >= ARRAY_SIZE(ps->vlans))
 		return -ERANGE;
 
 	/* Just do a sleeping operation to make lockdep checks effective */
-- 
2.29.2