net/ipv6/exthdrs.c: Strict PadN option checking (c1412fce) · Commits · 戴 / test

Added strict checking of PadN, as PadN can be used to increase header size and thus push the protocol header into the 2nd fragment. PadN is used to align the options within the Hop-by-Hop or Destination Options header to 64-bit boundaries. The maximum valid size is thus 7 bytes. RFC 4942 recommends to actively check the "payload" itself and ensure that it contains only zeroes. See also RFC 4942 section 2.1.9.5. Signed-off-by:

Eldad Zack <eldad@fogrefinery.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv6/exthdrs.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -153,6 +153,7 @@ static int ip6_parse_tlv(struct tlvtype_proc procs, struct sk_buff skb)

		while (len > 0) {
		int optlen = nh[off + 1] + 2;
		int i;

		switch (nh[off]) {
		case IPV6_TLV_PAD0:
		@@ -160,6 +161,21 @@ static int ip6_parse_tlv(struct tlvtype_proc procs, struct sk_buff skb)
		break;

		case IPV6_TLV_PADN:
		/* RFC 2460 states that the purpose of PadN is
		* to align the containing header to multiples
		* of 8. 7 is therefore the highest valid value.
		* See also RFC 4942, Section 2.1.9.5.
		*/
		if (optlen > 7)
		goto bad;
		/* RFC 4942 recommends receiving hosts to
		* actively check PadN payload to contain
		* only zeroes.
		*/
		for (i = 2; i < optlen; i++) {
		if (nh[off + i] != 0)
		goto bad;
		}
		break;

		default: /* Other TLV code so scan list */

Admin message