netdev - Re: [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0b2713a4e53f68f2636687c8caeb5a20803a2a1a.camel@redhat.com>
Date:   Thu, 24 Jun 2021 15:15:59 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse_tlv()

On Thu, 2021-06-24 at 03:07 -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> 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: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Fixes: c1412fce7ecc ("net/ipv6/exthdrs.c: Strict PadN option checking")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: Tom Herbert <tom@...bertland.com>
> ---
> v2: Removed not needed optlen assignment for IPV6_TLV_PAD1 handling,
>     added the Fixes: tag for first problem, feedback from Paolo, thanks !
> 
>  net/ipv6/exthdrs.c | 27 +++++++++++++--------------
>  1 file changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
> index 6f7da8f3e2e5849f917853984c69bf02a0f1e27c..26882e165c9e37a105f988020031f03d6b1a5cf9 100644
> --- a/net/ipv6/exthdrs.c
> +++ b/net/ipv6/exthdrs.c
> @@ -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;

LGTM!

Reviewd-by: Paolo Abeni <pabeni@...hat.com>