linux-kernel - Re: [PATCH review 5/6] userns: Allow the userns root to mount ramfs.

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Message-ID: <20130127182328.GB338@mail.hallyn.com>
Date:	Sun, 27 Jan 2013 18:23:28 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Linux Containers <containers@...ts.linux-foundation.org>,
	"Serge E. Hallyn" <serge@...lyn.com>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH review 5/6] userns: Allow the userns root to mount
 ramfs.

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> 
> There is no backing store to ramfs and file creation
> rules are the same as for any other filesystem so
> it is semantically safe to allow unprivileged users
> to mount it.
> 
> The memory control group successfully limits how much
> memory ramfs can consume on any system that cares about
> a user namespace root using ramfs to exhaust memory
> the memory control group can be deployed.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Acked-by: Serge Hallyn <serge.hallyn@...onical.com>

> ---
>  fs/ramfs/inode.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
> index eab8c09..c24f1e1 100644
> --- a/fs/ramfs/inode.c
> +++ b/fs/ramfs/inode.c
> @@ -260,6 +260,7 @@ static struct file_system_type ramfs_fs_type = {
>  	.name		= "ramfs",
>  	.mount		= ramfs_mount,
>  	.kill_sb	= ramfs_kill_sb,
> +	.fs_flags	= FS_USERNS_MOUNT,
>  };
>  static struct file_system_type rootfs_fs_type = {
>  	.name		= "rootfs",
> -- 
> 1.7.5.4
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