linux-kernel - Re: [BUG] Bug in netprio_cgroup and netcls

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Message-ID: <50FF287C.70906@gmail.com>
Date:	Tue, 22 Jan 2013 16:02:04 -0800
From:	John Fastabend <john.fastabend@...il.com>
To:	Daniel Wagner <wagi@...om.org>
CC:	Li Zefan <lizefan@...wei.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Neil Horman <nhorman@...driver.com>,
	Daniel Wagner <daniel.wagner@...-carit.de>,
	LKML <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [BUG] Bug in netprio_cgroup and netcls_cgroup ?

[...]

>>
>> OK, I guess we should do something similar in the netprio, netcls
>> cgroups and
>> yes document it as you noted in your last comment.
>
> Here is my attempt to add such a check. I really don't know if this is the
> correct way to do so. To test this I have written a test program, which
> seems to test the right thing. Please have a look and let me know if
> it is correct: http://www.monom.org/misc/scm_rights.c
>
> And here a dirty first version of the patch:
>
>
>  From 49a78d907eaf31c16673025e7e3b4844e419e416 Mon Sep 17 00:00:00 2001
> From: Daniel Wagner <daniel.wagner@...-carit.de>
> Date: Tue, 22 Jan 2013 11:08:22 +0100
> Subject: [PATCH] net: net_prio: Block attach if a socket is shared
>
> ---
>   net/core/netprio_cgroup.c | 30 ++++++++++++++++++++++++++++++
>   1 file changed, 30 insertions(+)
>
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index 847c02b..de4e6c5 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -274,9 +274,39 @@ static struct cftype ss_files[] = {
>   	{ }	/* terminate */
>   };
>
> +static int check_cnt(const void *v, struct file *file, unsigned n)
> +{
> +	unsigned *flag = (unsigned *)v;
> +	int err;
> +
> +	struct socket *sock = sock_from_file(file, &err);
> +	if (sock && file_count(file) > 1)
> +		*flag = 1;
> +

I think this check will catch a lot of cases that are not necessarily
sharing a socket across tasks though. For example iscsid passes a file
descriptor to the kernel which does a sockfd_lookup() incrementing
f_count. Similarly look at dup/clone/etc.

In many of these cases I believe it should be OK to move the task
around when the sockets are not shared between multiple tasks.

.John

-- 
John Fastabend         Intel Corporation
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