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ipv6: fix out-of-bound access in ip6_parse_tlv()

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First problem is that optlen is fetched without checking
there is more than one byte to parse.

Fix this by taking care of IPV6_TLV_PAD1 before
fetching optlen (under appropriate sanity checks against len)

Second problem is that IPV6_TLV_PADN checks of zero
padding are performed before the check of remaining length.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Fixes: c1412fce7e ("net/ipv6/exthdrs.c: Strict PadN option checking")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2021-06-24 03:07:20 -07:00 committed by David S. Miller
parent d9b6d26f65
commit 624085a31c
1 changed files with 13 additions and 14 deletions
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27
net/ipv6/exthdrs.c
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@ -135,18 +135,23 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
len -= 2;
while (len > 0) {
int optlen = nh[off + 1] + 2;
int i;
int optlen, i;
switch (nh[off]) {
case IPV6_TLV_PAD1:
optlen = 1;
if (nh[off] == IPV6_TLV_PAD1) {
padlen++;
if (padlen > 7)
goto bad;
break;
off++;
len--;
continue;
}
if (len < 2)
goto bad;
optlen = nh[off + 1] + 2;
if (optlen > len)
goto bad;
case IPV6_TLV_PADN:
if (nh[off] == 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.
@ -163,12 +168,7 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
if (nh[off + i] != 0)
goto bad;
}
break;
default: /* Other TLV code so scan list */
if (optlen > len)
goto bad;
} else {
tlv_count++;
if (tlv_count > max_count)
goto bad;
@ -188,7 +188,6 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
return false;
padlen = 0;
break;
}
off += optlen;
len -= optlen;