From 990a9d4975c974b05a8abaaeca5bbcfc55d31dcb Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 17 May 2018 15:33:36 +0300
Subject: net/ncsi: prevent a couple array underflows

We recently refactored this code and introduced a static checker
warning.  Smatch complains that if cmd->index is zero then we would
underflow the arrays.  That's obviously true.

The question is whether we prevent cmd->index from being zero at a
different level.  I've looked at the code and I don't immediately see
a check for that.

Fixes: 062b3e1b6d4f ("net/ncsi: Refactor MAC, VLAN filters")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/ncsi/ncsi-rsp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ncsi/ncsi-rsp.c b/net/ncsi/ncsi-rsp.c
index ce94979..a6b7c7d 100644
--- a/net/ncsi/ncsi-rsp.c
+++ b/net/ncsi/ncsi-rsp.c
@@ -347,7 +347,7 @@ static int ncsi_rsp_handler_svf(struct ncsi_request *nr)
 
 	cmd = (struct ncsi_cmd_svf_pkt *)skb_network_header(nr->cmd);
 	ncf = &nc->vlan_filter;
-	if (cmd->index > ncf->n_vids)
+	if (cmd->index == 0 || cmd->index > ncf->n_vids)
 		return -ERANGE;
 
 	/* Add or remove the VLAN filter. Remember HW indexes from 1 */
@@ -445,7 +445,8 @@ static int ncsi_rsp_handler_sma(struct ncsi_request *nr)
 	ncf = &nc->mac_filter;
 	bitmap = &ncf->bitmap;
 
-	if (cmd->index > ncf->n_uc + ncf->n_mc + ncf->n_mixed)
+	if (cmd->index == 0 ||
+	    cmd->index > ncf->n_uc + ncf->n_mc + ncf->n_mixed)
 		return -ERANGE;
 
 	index = (cmd->index - 1) * ETH_ALEN;
-- 
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