[PATCH RFC] Smack: Fix handling of IPv4 traffic received by PF_INET6 sockets

[Casey Schaufler]

On 7/10/2018 12:05 AM, Piotr Sawicki wrote:
> A socket which has sk_family set to PF_INET6 is able to receive not
> only IPv6 but also IPv4 traffic (IPv4-mapped IPv6 addresses).
>
> Prior to this patch, the smk_skb_to_addr_ipv6() could have been
> called for socket buffers containing IPv4 packets, in result such
> traffic was allowed.
>
> Signed-off-by: Piotr Sawicki <p.sawicki2 at partner.samsung.com>

Looks fine from here. Do you have a simple test case?

> ---
>   security/smack/smack_lsm.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 19de675..1315de4 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -3924,15 +3924,19 @@ static int smack_socket_sock_rcv_skb(struct sock 
> *sk, struct sk_buff *skb)
>   	struct smack_known *skp = NULL;
>   	int rc = 0;
>   	struct smk_audit_info ad;
> +	u16 family = sk->sk_family;
>   #ifdef CONFIG_AUDIT
>   	struct lsm_network_audit net;
>   #endif
>   #if IS_ENABLED(CONFIG_IPV6)
>   	struct sockaddr_in6 sadd;
>   	int proto;
> +
> +	if (family == PF_INET6 && skb->protocol == htons(ETH_P_IP))
> +		family = PF_INET;
>   #endif /* CONFIG_IPV6 */
>
> -	switch (sk->sk_family) {
> +	switch (family) {
>   	case PF_INET:
>   #ifdef CONFIG_SECURITY_SMACK_NETFILTER
>   		/*
> @@ -3950,7 +3954,7 @@ static int smack_socket_sock_rcv_skb(struct sock 
> *sk, struct sk_buff *skb)
>   		 */
>   		netlbl_secattr_init(&secattr);
>
> -		rc = netlbl_skbuff_getattr(skb, sk->sk_family, &secattr);
> +		rc = netlbl_skbuff_getattr(skb, family, &secattr);
>   		if (rc == 0)
>   			skp = smack_from_secattr(&secattr, ssp);
>   		else
> @@ -3963,7 +3967,7 @@ static int smack_socket_sock_rcv_skb(struct sock 
> *sk, struct sk_buff *skb)
>   #endif
>   #ifdef CONFIG_AUDIT
>   		smk_ad_init_net(&ad, __func__, LSM_AUDIT_DATA_NET, &net);
> -		ad.a.u.net->family = sk->sk_family;
> +		ad.a.u.net->family = family;
>   		ad.a.u.net->netif = skb->skb_iif;
>   		ipv4_skb_to_auditdata(skb, &ad.a, NULL);
>   #endif
> @@ -3977,7 +3981,7 @@ static int smack_socket_sock_rcv_skb(struct sock 
> *sk, struct sk_buff *skb)
>   		rc = smk_bu_note("IPv4 delivery", skp, ssp->smk_in,
>   					MAY_WRITE, rc);
>   		if (rc != 0)
> -			netlbl_skbuff_err(skb, sk->sk_family, rc, 0);
> +			netlbl_skbuff_err(skb, family, rc, 0);
>   		break;
>   #if IS_ENABLED(CONFIG_IPV6)
>   	case PF_INET6:

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