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Commit 9b905fe6 authored by Eldad Zack's avatar Eldad Zack Committed by David S. Miller
Browse files

ipv6/exthdrs: strict Pad1 and PadN check 



The following tightens the padding check from commit
c1412fce :

* Take into account combinations of consecutive Pad1 and PadN.

* Catch the corner case of when only padding is present in the
  header, when the extention header length is 0 (i.e., 8 bytes).
  In this case, the header would have exactly 6 bytes of padding:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:  Next Header  : Hdr Ext Len=0 :                               :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
:                        Padding (Pad1 or PadN)                 :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Signed-off-by: default avatarEldad Zack <eldad@fogrefinery.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f7142e6c

net/ipv6/exthdrs.c

+14 −1
Original line number Diff line number Diff line
@@ -144,6 +144,7 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs, struct sk_buff *skb) 
	const unsigned char *nh = skb_network_header(skb);

	int off = skb_network_header_len(skb);

	int len = (skb_transport_header(skb)[1] + 1) << 3;

	int padlen = 0;



	if (skb_transport_offset(skb) + len > skb_headlen(skb))

		goto bad;
@@ -158,6 +159,9 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs, struct sk_buff *skb) 
		switch (nh[off]) {

		case IPV6_TLV_PAD1:

			optlen = 1;

			padlen++;

			if (padlen > 7)

				goto bad;

			break;



		case IPV6_TLV_PADN:
@@ -166,7 +170,8 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs, struct sk_buff *skb) 
			 * of 8. 7 is therefore the highest valid value.

			 * See also RFC 4942, Section 2.1.9.5.

			 */

			if (optlen > 7)

			padlen += optlen;

			if (padlen > 7)

				goto bad;

			/* RFC 4942 recommends receiving hosts to

			 * actively check PadN payload to contain
@@ -195,11 +200,19 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs, struct sk_buff *skb) 
				if (ip6_tlvopt_unknown(skb, off) == 0)

					return false;

			}

			padlen = 0;

			break;

		}

		off += optlen;

		len -= optlen;

	}

	/* This case will not be caught by above check since its padding

	 * length is smaller than 7:

	 * 1 byte NH + 1 byte Length + 6 bytes Padding

	 */

	if ((padlen == 6) && ((off - skb_network_header_len(skb)) == 8))

		goto bad;



	if (len == 0)

		return true;

bad: