Re: [PATCH net] ipv6: Fix out-of-bounds access in ipv6_find_tlv()

[David Ahern <dsahern@kernel.org>]

On 5/23/23 2:29 AM, Gavrilov Ilia wrote:
> optlen is fetched without checking whether there is more than one byte to parse.
> It can lead to out-of-bounds access.
> 
> Found by InfoTeCS on behalf of Linux Verification Center
> (linuxtesting.org) with SVACE.
> 
> Fixes: 3c73a0368e99 ("ipv6: Update ipv6 static library with newly needed functions")

That is not the right Fixes tag; that commit only moved the code.

Fixes: c61a40432509 ("[IPV6]: Find option offset by type.")

> Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru>
> ---
>  net/ipv6/exthdrs_core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/ipv6/exthdrs_core.c b/net/ipv6/exthdrs_core.c
> index da46c4284676..49e31e4ae7b7 100644
> --- a/net/ipv6/exthdrs_core.c
> +++ b/net/ipv6/exthdrs_core.c
> @@ -143,6 +143,8 @@ int ipv6_find_tlv(const struct sk_buff *skb, int offset, int type)
>  			optlen = 1;
>  			break;
>  		default:
> +			if (len < 2)
> +				goto bad;
>  			optlen = nh[offset + 1] + 2;
>  			if (optlen > len)
>  				goto bad;

Reviewed-by: David Ahern <dsahern@kernel.org>