linux-kernel - Re: [PATCH 1/3] lib/kobject_uevent.c: disable broadcast of uevents to other namespaces

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Message-ID: <87zj0tyeq3.fsf@x220.int.ebiederm.org>
Date:	Thu, 10 Sep 2015 19:36:04 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Michael J. Coss" <michael.coss@...atel-lucent.com>
Cc:	gregkh@...uxfoundation.org, davem@...emloft.net,
	linux-kernel@...r.kernel.org, containers@...ts.linuxcontainers.org,
	serge.hallyn@...ntu.com, stgraber@...ntu.com
Subject: Re: [PATCH 1/3] lib/kobject_uevent.c: disable broadcast of uevents to other namespaces

"Michael J. Coss" <michael.coss@...atel-lucent.com> writes:

> Restrict sending uevents to only those listeners operating in the same
> network namespace as the system init process.  This is the first step
> toward allowing policy control of the forwarding of events to other
> namespaces in userspace.

This limitation whould be better if we only skipped network namespaces
where you are sending spoofed uevents.

As it sits this has the possibility to break userspace.

Eric

> Signed-off-by: Michael J. Coss <michael.coss@...atel-lucent.com>
> ---
>  lib/kobject_uevent.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index f6c2c1e..d791e33 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -295,6 +295,10 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
>  		if (!netlink_has_listeners(uevent_sock, 1))
>  			continue;
>  
> +		/* forward event only to the host systems network namespaces */
> +		if (!net_eq(sock_net(uevent_sock), &init_net))
> +			continue;
> +
>  		/* allocate message with the maximum possible size */
>  		len = strlen(action_string) + strlen(devpath) + 2;
>  		skb = alloc_skb(len + env->buflen, GFP_KERNEL);
--
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