Quoting Miklos Szeredi (miklos@szeredi.hu):
> From: Miklos Szeredi <mszeredi@suse.cz>
> 
> If CLONE_NEWNS and CLONE_NEWNS_USERMNT are given to clone(2) or
> unshare(2), then allow user mounts within the new namespace.
> 
> This is not flexible enough, because user mounts can't be enabled for
> the initial namespace.
> 
> The remaining clone bits also getting dangerously few...
> 
> Alternatives are:
> 
>   - prctl() flag
>   - setting through the containers filesystem

Sorry, I know I had mentioned it, but this is definately my least
favorite approach.

Curious whether are any other suggestions/opinions from the containers
list?

thanks,
-serge

> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
> ---
> 
> Index: linux/fs/namespace.c
> ===================================================================
> --- linux.orig/fs/namespace.c	2007-04-12 13:46:19.000000000 +0200
> +++ linux/fs/namespace.c	2007-04-12 13:54:36.000000000 +0200
> @@ -1617,6 +1617,8 @@ struct mnt_namespace *copy_mnt_ns(int fl
>  		return ns;
> 
>  	new_ns = dup_mnt_ns(ns, new_fs);
> +	if (new_ns && (flags & CLONE_NEWNS_USERMNT))
> +		new_ns->flags |= MNT_NS_PERMIT_USERMOUNTS;
> 
>  	put_mnt_ns(ns);
>  	return new_ns;
> Index: linux/include/linux/sched.h
> ===================================================================
> --- linux.orig/include/linux/sched.h	2007-04-12 13:26:48.000000000 +0200
> +++ linux/include/linux/sched.h	2007-04-12 13:54:36.000000000 +0200
> @@ -26,6 +26,7 @@
>  #define CLONE_STOPPED		0x02000000	/* Start in stopped state */
>  #define CLONE_NEWUTS		0x04000000	/* New utsname group? */
>  #define CLONE_NEWIPC		0x08000000	/* New ipcs */
> +#define CLONE_NEWNS_USERMNT	0x10000000	/* Allow user mounts in ns? */
> 
>  /*
>   * Scheduling policies
> Index: linux/kernel/fork.c
> ===================================================================
> --- linux.orig/kernel/fork.c	2007-04-11 18:27:46.000000000 +0200
> +++ linux/kernel/fork.c	2007-04-12 13:59:10.000000000 +0200
> @@ -1586,7 +1586,7 @@ asmlinkage long sys_unshare(unsigned lon
>  	err = -EINVAL;
>  	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
>  				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
> -				CLONE_NEWUTS|CLONE_NEWIPC))
> +				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNS_USERMNT))
>  		goto bad_unshare_out;
> 
>  	if ((err = unshare_thread(unshare_flags)))
> 
> --
> -
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