On 06/01/2016 03:18 PM, Eric Dumazet wrote:
> On Wed, 2016-06-01 at 15:01 -0400, Paul Moore wrote:
>> Hello,
>>
>> I'm currently trying to debug a problem with 4.7-rc1 and labeled
>> networking over UDP. I'm having some difficulty with the latest
>> 4.7-rc1 builds on my test system at the moment so I haven't been able
>> to concisely identify the problem, but looking through the commits in
>> 4.7-rc1 I think there may be a problem with the following:
>>
>> commit e6afc8ace6dd5cef5e812f26c72579da8806f5ac
>> Author: samanthakumar <samanthakumar@xxxxxxxxxx>
>> Date: Tue Apr 5 12:41:15 2016 -0400
>>
>> udp: remove headers from UDP packets before queueing
>>
>> Remove UDP transport headers before queueing packets for reception.
>> This change simplifies a follow-up patch to add MSG_PEEK support.
>>
>> Signed-off-by: Sam Kumar <samanthakumar@xxxxxxxxxx>
>> Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
>> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
>>
>> ... it appears that this commit changes things so that sk_filter() is
>> only called when sk->sk_filter is not NULL. While this is fine for
>> the traditional socket filter case, it causes problems with LSMs that
>> make use of security_sock_rcv_skb() to enforce per-packet access
>> controls.
>>
>> Hopefully I'll get 4.7-rc1 booting soon and I can do a proper
>> bisection test around this patch, but I wanted to mention this now in
>> case others are seeing the same problem.
>>
>
> Thanks for the report. Please try following fix.
>
> sk_filter() got additional features like the skb_pfmemalloc() things and
> security_sock_rcv_skb()
This resolved the SELinux regression for me.
Tested-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index d56c0559b477..0ff31d97d485 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1618,12 +1618,12 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
> }
> }
>
> - if (rcu_access_pointer(sk->sk_filter)) {
> - if (udp_lib_checksum_complete(skb))
> + if (rcu_access_pointer(sk->sk_filter) &&
> + udp_lib_checksum_complete(skb))
> goto csum_error;
> - if (sk_filter(sk, skb))
> - goto drop;
> - }
> +
> + if (sk_filter(sk, skb))
> + goto drop;
>
> udp_csum_pull_header(skb);
> if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 2da1896af934..f421c9f23c5b 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -653,12 +653,12 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
> }
> }
>
> - if (rcu_access_pointer(sk->sk_filter)) {
> - if (udp_lib_checksum_complete(skb))
> - goto csum_error;
> - if (sk_filter(sk, skb))
> - goto drop;
> - }
> + if (rcu_access_pointer(sk->sk_filter) &&
> + udp_lib_checksum_complete(skb))
> + goto csum_error;
> +
> + if (sk_filter(sk, skb))
> + goto drop;
>
> udp_csum_pull_header(skb);
> if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
>
>
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