net: dsa: bcm_sf2: Fix overflow checks

Commit f949a12 ("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: f949a12 ("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>

drivers/net/dsa/bcm_sf2_cfp.c

@@ -882,17 +882,14 @@ 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;
-
 	ret = bcm_sf2_cfp_rule_cmp(priv, port, fs);
 	if (ret == 0)
 		return -EEXIST;
@@ -973,7 +970,7 @@ static int bcm_sf2_cfp_rule_del(struct bcm_sf2_priv *priv, int port, u32 loc)
 	struct cfp_rule *rule;
 	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