linux-kernel - [PATCH 3.2 56/59] ipv6: avoid overflow of offset in ip6_find

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1503061993.629698818@decadent.org.uk>
Date:   Fri, 18 Aug 2017 14:13:13 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
        "Sabrina Dubroca" <sd@...asysnail.net>,
        "Hannes Frederic Sowa" <hannes@...essinduktion.org>
Subject: [PATCH 3.2 56/59] ipv6: avoid overflow of offset in
 ip6_find_1stfragopt

3.2.92-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Sabrina Dubroca <sd@...asysnail.net>

commit 6399f1fae4ec29fab5ec76070435555e256ca3a6 upstream.

In some cases, offset can overflow and can cause an infinite loop in
ip6_find_1stfragopt(). Make it unsigned int to prevent the overflow, and
cap it at IPV6_MAXPLEN, since packets larger than that should be invalid.

This problem has been here since before the beginning of git history.

Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/ipv6/ip6_output.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -561,13 +561,14 @@ static void ip6_copy_metadata(struct sk_
 
 int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 {
-	u16 offset = sizeof(struct ipv6hdr);
+	unsigned int offset = sizeof(struct ipv6hdr);
 	unsigned int packet_len = skb->tail - skb->network_header;
 	int found_rhdr = 0;
 	*nexthdr = &ipv6_hdr(skb)->nexthdr;
 
 	while (offset <= packet_len) {
 		struct ipv6_opt_hdr *exthdr;
+		unsigned int len;
 
 		switch (**nexthdr) {
 
@@ -593,7 +594,10 @@ int ip6_find_1stfragopt(struct sk_buff *
 
 		exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
 						 offset);
-		offset += ipv6_optlen(exthdr);
+		len = ipv6_optlen(exthdr);
+		if (len + offset >= IPV6_MAXPLEN)
+			return -EINVAL;
+		offset += len;
 		*nexthdr = &exthdr->nexthdr;
 	}