netdev - Re: [PATCH net-next] bpf, skb_do_redirect: clear sender

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: <5617FA5A.9090406@iogearbox.net>
Date:	Fri, 09 Oct 2015 19:33:14 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Alexei Starovoitov <ast@...mgrid.com>,
	"Devon H. O'Dell" <dho@...tly.com>
CC:	davem@...emloft.net, edumazet@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] bpf, skb_do_redirect: clear sender_cpu before
 xmit

On 10/09/2015 04:35 AM, Alexei Starovoitov wrote:
> On 10/8/15 5:50 PM, Devon H. O'Dell wrote:
>>> with the amount of skb_sender_cpu_clear() all over the code base
>>> >I wonder whether there is a better solution to all of these.
>> I think there is. We found that splitting the union of sender_cpu and
>> napi_id solved the issue for us. In general, I think this is an OK
>> solution as long as the following hold:
>>
>>   * skbs are always allocated via kzalloc
>>   * out -> out cloned skbs are always cloned on the same CPU
>>   * an extra four bytes in skbuff isn't a bad thing
>
> I'm pretty sure extending sk_buff for this is not acceptable.

+1, I agree.

> I was thinking may be we can use sign bit to distinguish between
> napi_id and sender_cpu.
> Like:
>          if ((int)skb->sender_cpu >= 0)
>                  skb->sender_cpu = - (raw_smp_processor_id() + 1);
> and inside get_xps_queue() use it only if it's negative.
> Then we can remove skb_sender_cpu_clear() from everywhere.
> Adding a check to napi_hash_add() to make sure that napi_id is not
> negative is probably ok too.
> Thoughts?

I think this doesn't make it any more maintainable.

skb_sender_cpu_clear(), one can at least git-grep to easily find
out and review call-sites in the code. There are various members
already used differently depending on the context.

Thanks,
Daniel
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html