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| author | Eldad Zack <eldad@fogrefinery.com> | 2012-05-20 01:59:33 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-05-20 16:58:39 -0400 |
| commit | 9b905fe68433378032b851c4d81a59187689fa52 (patch) | |
| tree | 307801197cf9ce8b520a026962bf1e73f0019f9f /net | |
| parent | f7142e6c226076fd40c2ebaad9fb0c9a631b790e (diff) | |
| download | lwn-9b905fe68433378032b851c4d81a59187689fa52.tar.gz lwn-9b905fe68433378032b851c4d81a59187689fa52.zip | |
ipv6/exthdrs: strict Pad1 and PadN check
The following tightens the padding check from commit
c1412fce7eccae62b4de22494f6ab3ff8a90c0c6 :
* 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: Eldad Zack <eldad@fogrefinery.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv6/exthdrs.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c index 50ec95f9aeeb..6447dc49429f 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -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: |