netdev - Re: [PATCH] memory leak in netlink user->kernel processing

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Message-ID: <47010B07.5060009@gmail.com>
Date:	Mon, 01 Oct 2007 18:58:15 +0400
From:	"Denis V. Lunev" <dlunev@...il.com>
To:	Patrick McHardy <kaber@...sh.net>
CC:	"Denis V. Lunev" <den@...nvz.org>, davem@...emloft.net,
	netdev@...r.kernel.org, "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] memory leak in netlink user->kernel processing

Patrick McHardy wrote:
> Denis V. Lunev wrote:
>> netlink_kernel_create can be called with NULL as an input callback in several
>> places, f.e. in kobject_uevent_init. This means that if one sends packet from
>> user to kernel for such a socket, the packet will be leaked in the socket
>> queue forever.
>>
>> This patch adds a simple generic cleanup callback for these sockets.
> 
> 
> This should already be handled by netlink_getsockbypid:
> 
>         /* Don't bother queuing skb if kernel socket has no input
> function */
>         nlk = nlk_sk(sock);
>         if ((nlk->pid == 0 && !nlk->data_ready) ||
>             (sock->sk_state == NETLINK_CONNECTED &&
>              nlk->dst_pid != nlk_sk(ssk)->pid)) {
>                 sock_put(sock);
>                 return ERR_PTR(-ECONNREFUSED);
>         }
> -
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> 

Looks so...

By the way, Patrick, this looks like nlk->pid == 0 if and only if this
is a kernel socket. Right?

I have told with Alexey Kuznetsov and we have discrovered a way to get
rid of
        skb_queue_tail(&sk->sk_receive_queue, skb);
        sk->sk_data_ready(sk, len);
in netlink_sendskb/etc for kernel sockets and make user->kernel packets
processing truly synchronous.

The idea is simple, we should queue/wakeup in kernel->user direction and
simply call nlk->data_ready for user->kernel direction. This will remove
all the crap we have now. But we need a mark to determine the direction.
Which one will be better? (nlk->data_ready) or (nlk->pid == 0)

Regards,
	Den
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