netdev - Re: [PATCH net-next] fix unsafe set_memory

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Date:	Wed, 2 Oct 2013 21:44:17 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Xi Wang <xi.wang@...il.com>, x86@...nel.org,
	Eric Dumazet <edumazet@...gle.com>,
	linux-kernel@...r.kernel.org,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH net-next] fix unsafe set_memory_rw from softirq

On Wed, Oct 2, 2013 at 9:23 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Wed, 2013-10-02 at 20:50 -0700, Alexei Starovoitov wrote:
>> on x86 system with net.core.bpf_jit_enable = 1
>
>> diff --git a/include/linux/filter.h b/include/linux/filter.h
>> index a6ac848..378fa03 100644
>> --- a/include/linux/filter.h
>> +++ b/include/linux/filter.h
>> @@ -27,6 +27,7 @@ struct sk_filter
>>       unsigned int            len;    /* Number of filter blocks */
>>       unsigned int            (*bpf_func)(const struct sk_buff *skb,
>>                                           const struct sock_filter *filter);
>> +     struct work_struct      work;
>>       struct rcu_head         rcu;
>>       struct sock_filter      insns[0];
>>  };
>
> Nice catch !
>
> It seems only x86 and s390 needs this work_struct.

I think ifdef config_x86 is a bit ugly inside struct sk_filter, but
don't mind whichever way.

> (and you might CC Heiko Carstens <heiko.carstens@...ibm.com> to ask him
> to make the s390 part, of Ack it if you plan to do it)

set_memory_rw() on s390 is a simple page table walker that doesn't do
any IPI unlike x86
Heiko, please confirm that it's not an issue there.

Thanks
Alexei
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