linux-kernel - Re: [PATCH 1/1] devices cgroup: allow mkfifo

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Date:	Thu, 11 Dec 2008 19:12:08 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	torvalds@...ux-foundation.org, lkml <linux-kernel@...r.kernel.org>,
	stable@...nel.org, Pavel Emelyanov <xemul@...nvz.org>,
	Daniel Lezcano <dlezcano@...ibm.com>
Subject: Re: [PATCH 1/1] devices cgroup: allow mkfifo

On Thu, 11 Dec 2008 09:50:27 -0600 "Serge E. Hallyn" <serue@...ibm.com> wrote:

> The devcgroup_inode_permission() hook in the devices whitelist
> cgroup has always bypassed access checks on fifos.  But the
> mknod hook did not.  The devices whitelist is only about block
> and char devices, and fifos can't even be added to the whitelist,
> so fifos can't be created at all except by tasks which have 'a'
> in their whitelist (meaning they have access to all devices).
> 
> Fix the behavior by bypassing access checks to mkfifo (and mksock).
> 
> (Thanks, Daniel, for finding this)
> 
> Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
> Reviewed-by: Li Zefan <lizf@...fujitsu.com>
> ---
>  security/device_cgroup.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index 5ba7870..df9d491 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -513,6 +513,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
>  	struct dev_cgroup *dev_cgroup;
>  	struct dev_whitelist_item *wh;
>  
> +	if (!S_ISBLK(mode) && !S_ISCHR(mode))
> +		return 0;
> +
>  	rcu_read_lock();
>  
>  	dev_cgroup = task_devcgroup(current);

hm.  I'd looked at your description and decided this was 2.6.29 material.

But you think it's for 2.6.28 and even for 2.6.27.  How come?

(iow, your changelog sucked :)
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