From d1c53c8e870cdedb6fc9550f41c558bab45b5219 Mon Sep 17 00:00:00 2001 From: Werner Almesberger Date: Fri, 2 Aug 2013 10:51:34 -0300 Subject: [PATCH] icmpv6_filter: allow ICMPv6 messages with bodies < 4 bytes By using sizeof(_hdr), net/ipv6/raw.c:icmpv6_filter implicitly assumes that any valid ICMPv6 message is at least eight bytes long, i.e., that the message body is at least four bytes. The DIS message of RPL (RFC 6550 section 6.2, from the 6LoWPAN world), has a minimum length of only six bytes, and is thus blocked by icmpv6_filter. RFC 4443 seems to allow even a zero-sized body, making the minimum allowable message size four bytes. Signed-off-by: Werner Almesberger Signed-off-by: David S. Miller --- net/ipv6/raw.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c index 164fb5f58641..c1e533498203 100644 --- a/net/ipv6/raw.c +++ b/net/ipv6/raw.c @@ -63,6 +63,8 @@ #include #include +#define ICMPV6_HDRLEN 4 /* ICMPv6 header, RFC 4443 Section 2.1 */ + static struct raw_hashinfo raw_v6_hashinfo = { .lock = __RW_LOCK_UNLOCKED(raw_v6_hashinfo.lock), }; @@ -111,8 +113,11 @@ static int icmpv6_filter(const struct sock *sk, const struct sk_buff *skb) struct icmp6hdr _hdr; const struct icmp6hdr *hdr; + /* We require only the four bytes of the ICMPv6 header, not any + * additional bytes of message body in "struct icmp6hdr". + */ hdr = skb_header_pointer(skb, skb_transport_offset(skb), - sizeof(_hdr), &_hdr); + ICMPV6_HDRLEN, &_hdr); if (hdr) { const __u32 *data = &raw6_sk(sk)->filter.data[0]; unsigned int type = hdr->icmp6_type; -- 2.20.1