[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 <redacted>
---
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

On 1/19/2021 6:53 AM, Dan Carpenter wrote:

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 <redacted>

Acked-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Tue, 19 Jan 2021 17:53:35 +0300 you wrote:

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 <redacted>

[...]

Here is the summary with links:
  - [net-next] net: dsa: Fix off by one in dsa_loop_port_vlan_add()
    https://git.kernel.org/netdev/net-next/c/646188c9550f

You are awesome, thank you!
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