From: Alexander Aring <alex.aring@gmail.com>
Date: Sat, 4 Apr 2020 11:22:57 -0400
Subject: ipv6: rpl: fix loop iteration
Patch-mainline: v5.7-rc1
Git-commit: a7f9a6f4cc5fb4d5c5a03f3f898b7cb86db05cbf
References: bsc#1176447

This patch fix the loop iteration by not walking over the last
iteration. The cmpri compressing value exempt the last segment. As the
code shows the last iteration will be overwritten by cmpre value
handling which is for the last segment.

I think this doesn't end in any bufferoverflows because we work on worst
case temporary buffer sizes but it ends in not best compression settings
in some cases.

Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr")
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/ipv6/rpl.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/ipv6/rpl.c
+++ b/net/ipv6/rpl.c
@@ -48,7 +48,7 @@ void ipv6_rpl_srh_decompress(struct ipv6
 	outhdr->cmpri = 0;
 	outhdr->cmpre = 0;
 
-	for (i = 0; i <= n; i++)
+	for (i = 0; i < n; i++)
 		ipv6_rpl_addr_decompress(&outhdr->rpl_segaddr[i], daddr,
 					 ipv6_rpl_segdata_pos(inhdr, i),
 					 inhdr->cmpri);
@@ -66,7 +66,7 @@ static unsigned char ipv6_rpl_srh_calc_c
 	int i;
 
 	for (plen = 0; plen < sizeof(*daddr); plen++) {
-		for (i = 0; i <= n; i++) {
+		for (i = 0; i < n; i++) {
 			if (daddr->s6_addr[plen] !=
 			    inhdr->rpl_segaddr[i].s6_addr[plen])
 				return plen;
@@ -114,7 +114,7 @@ void ipv6_rpl_srh_compress(struct ipv6_r
 	outhdr->cmpri = cmpri;
 	outhdr->cmpre = cmpre;
 
-	for (i = 0; i <= n; i++)
+	for (i = 0; i < n; i++)
 		ipv6_rpl_addr_compress(ipv6_rpl_segdata_pos(outhdr, i),
 				       &inhdr->rpl_segaddr[i], cmpri);