On Wed, Jun 1, 2016 at 4:44 PM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
> 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>
The patch works for me too. Eric, are you going to send this to DaveM
(assuming he isn't listening in on this thread and picking it up
himself)?
Tested-by: Paul Moore <paul@xxxxxxxxxxxxxx>
>> 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)) {
>>
>>
--
paul moore
www.paul-moore.com
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