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Re: [PATCH] can: Fix kernel panic at security_sock_rcv_skb

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On 01/12/2017 02:01 PM, Eric Dumazet wrote:
> On Thu, 2017-01-12 at 09:22 +0100, Oliver Hartkopp wrote:

>> But my main concern is:
>>
>> The reason why can_rx_delete_receiver() was introduced was the need to
>> remove a huge number of receivers with can_rx_unregister().
>>
>> When you call synchronize_rcu() after each receiver removal this would
>> potentially lead to a big performance issue when e.g. closing CAN_RAW
>> sockets with a high number of receivers.
>>
>> So the idea was to remove/unlink the receiver hlist_del_rcu(&r->list)
>> and also kmem_cache_free(rcv_cache, r) by some rcu mechanism - so that
>> all elements are cleaned up by rcu at a later point.
>>
>> Is it possible that the problems emerge due to hlist_del_rcu(&r->list)
>> and you accidently fix it with your introduced synchronize_rcu()?
>
> I agree this patch does not fix the root cause.
>
> The main problem seems that the sockets themselves are not RCU
> protected.
>
> If CAN uses RCU for delivery, then sockets should be freed only after
> one RCU grace period.
>
> On recent kernels, following patch could help :
>

Thanks Eric!

@Liu ShuoX: Can you check if Eric's suggestion fixes the issue in your 
setup?

Best regards,
Oliver

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Thread

[PATCH] can: Fix kernel panic at security_sock_rcv_skb Liu ShuoX <shuo.a.liu@intel.com> - 2017-01-12 07:40 +0100
  Re: [PATCH] can: Fix kernel panic at security_sock_rcv_skb Oliver Hartkopp <socketcan@hartkopp.net> - 2017-01-12 09:30 +0100
    Re: [PATCH] can: Fix kernel panic at security_sock_rcv_skb Eric Dumazet <eric.dumazet@gmail.com> - 2017-01-12 14:10 +0100
      Re: [PATCH] can: Fix kernel panic at security_sock_rcv_skb Oliver Hartkopp <socketcan@hartkopp.net> - 2017-01-12 17:40 +0100
        Re: [PATCH] can: Fix kernel panic at security_sock_rcv_skb Liu Shuo <shuo.a.liu@intel.com> - 2017-01-14 04:50 +0100
          Re: [PATCH] can: Fix kernel panic at security_sock_rcv_skb Oliver Hartkopp <socketcan@hartkopp.net> - 2017-01-14 15:00 +0100
            Re: [PATCH] can: Fix kernel panic at security_sock_rcv_skb Eric Dumazet <eric.dumazet@gmail.com> - 2017-01-14 18:40 +0100

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