From 9b7346bb79a38d6de21b9c24a42314b7fcce6953 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Fri, 18 Aug 2017 14:40:53 +0200 Subject: [PATCH] ipv6: accept 64k - 1 packet length in ip6_find_1stfragopt() commit 3de33e1ba0506723ab25734e098cf280ecc34756 upstream. A packet length of exactly IPV6_MAXPLEN is allowed, we should refuse parsing options only if the size is 64KiB or more. While at it, remove one extra variable and one assignment which were also introduced by the commit that introduced the size check. Checking the sum 'offset + len' and only later adding 'len' to 'offset' doesn't provide any advantage over directly summing to 'offset' and checking it. Fixes: 6399f1fae4ec ("ipv6: avoid overflow of offset in ip6_find_1stfragopt") Signed-off-by: Stefano Brivio Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv6/output_core.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c index 720b82a84d6b..ab59ecd95139 100644 --- a/net/ipv6/output_core.c +++ b/net/ipv6/output_core.c @@ -16,7 +16,6 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr) while (offset <= packet_len) { struct ipv6_opt_hdr *exthdr; - unsigned int len; switch (**nexthdr) { @@ -42,10 +41,9 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr) exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) + offset); - len = ipv6_optlen(exthdr); - if (len + offset >= IPV6_MAXPLEN) + offset += ipv6_optlen(exthdr); + if (offset > IPV6_MAXPLEN) return -EINVAL; - offset += len; *nexthdr = &exthdr->nexthdr; }