net: dsa: bcm_sf2: Fix overflow checks

commit d0802dc4 upstream.

Commit f949a12f ("net: dsa: bcm_sf2: fix buffer overflow doing
set_rxnfc") tried to fix the some user controlled buffer overflows in
bcm_sf2_cfp_rule_set() and bcm_sf2_cfp_rule_del() but the fix was using
CFP_NUM_RULES, which while it is correct not to overflow the bitmaps, is
not representative of what the device actually supports. Correct that by
using bcm_sf2_cfp_rule_size() instead.

The latter subtracts the number of rules by 1, so change the checks from
greater than or equal to greater than accordingly.

Fixes: f949a12f ("net: dsa: bcm_sf2: fix buffer overflow doing set_rxnfc")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/dsa/bcm_sf2_cfp.c

@@ -742,17 +742,14 @@ static int bcm_sf2_cfp_rule_set(struct dsa_switch *ds, int port,
 	     fs->m_ext.data[1]))
 		return -EINVAL;
 
-	if (fs->location != RX_CLS_LOC_ANY && fs->location >= CFP_NUM_RULES)
+	if (fs->location != RX_CLS_LOC_ANY &&
+	    fs->location > bcm_sf2_cfp_rule_size(priv))
 		return -EINVAL;
 
 	if (fs->location != RX_CLS_LOC_ANY &&
 	    test_bit(fs->location, priv->cfp.used))
 		return -EBUSY;
 
-	if (fs->location != RX_CLS_LOC_ANY &&
-	    fs->location > bcm_sf2_cfp_rule_size(priv))
-		return -EINVAL;
-
 	/* This rule is a Wake-on-LAN filter and we must specifically
 	 * target the CPU port in order for it to be working.
 	 */
@@ -839,7 +836,7 @@ static int bcm_sf2_cfp_rule_del(struct bcm_sf2_priv *priv, int port,
 	u32 next_loc = 0;
 	int ret;
 
-	if (loc >= CFP_NUM_RULES)
+	if (loc > bcm_sf2_cfp_rule_size(priv))
 		return -EINVAL;
 
 	/* Refuse deleting unused rules, and those that are not unique since