linux-kernel - Re: [PATCH] proc connector: reject unprivileged listener bumps

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Message-Id: <20130227.130859.1239743436839936054.davem@davemloft.net>
Date:	Wed, 27 Feb 2013 13:08:59 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	matthltc@...ux.vnet.ibm.com
Cc:	keescook@...omium.org, linux-kernel@...r.kernel.org,
	zbr@...emap.net, netdev@...r.kernel.org, matthltc@...ibm.com
Subject: Re: [PATCH] proc connector: reject unprivileged listener bumps

From: Matt Helsley <matthltc@...ux.vnet.ibm.com>
Date: Tue, 26 Feb 2013 09:24:41 -0800

> On Mon, Feb 25, 2013 at 11:32:25PM -0800, Kees Cook wrote:
>> While PROC_CN_MCAST_LISTEN/IGNORE is entirely advisory, it was possible
>> for an unprivileged user to turn off notifications for all listeners by
>> sending PROC_CN_MCAST_IGNORE. Instead, require the same privileges as
>> required for a multicast bind.
>> 
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> Cc: Evgeniy Polyakov <zbr@...emap.net>
>> Cc: Matt Helsley <matthltc@...ibm.com>
>> Cc: stable@...r.kernel.org
>> ---
>>  drivers/connector/cn_proc.c |    8 ++++++++
>>  1 file changed, 8 insertions(+)
>> 
>> diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
>> index fce2000..1110478 100644
>> --- a/drivers/connector/cn_proc.c
>> +++ b/drivers/connector/cn_proc.c
>> @@ -313,6 +313,12 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>>  	    (task_active_pid_ns(current) != &init_pid_ns))
>>  		return;
>> 
>> +	/* Can only change if privileged. */
> 
> I think this comment doesn't tell us anything above and beyond the
> what capability check already tells us. I think you could improve it
> by noting that since the connector is multicast and not namespace-safe
> it's not yet appropriate to use ns_capable() here.
> 
> Acked-by: Matt Helsley <matthltc@...ibm.com>

Applied.
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