Re: [PATCH] Deny external checkpoint unless frozen

["Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Quoting Sukadev Bhattiprolu (sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org):
> 
> From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> Date: Sat, 21 Feb 2009 11:17:07 -0800
> Subject: [PATCH] Deny external checkpoint unless task is frozen
> 
> Remove a 'FIXME' and ensure that the tasks we are checkpointing are
> frozen unless its a self-checkpoint.
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>

Agreed.  I personally would like to just get rid of support
for t==current, but don't expect to get anywhere with that
argument :)

Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

> ---
>  checkpoint/checkpoint.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
> index 2bbb409..023bd9d 100644
> --- a/checkpoint/checkpoint.c
> +++ b/checkpoint/checkpoint.c
> @@ -19,6 +19,7 @@
>  #include <linux/mount.h>
>  #include <linux/utsname.h>
>  #include <linux/magic.h>
> +#include <linux/freezer.h>
>  #include <linux/checkpoint.h>
>  #include <linux/checkpoint_hdr.h>
> 
> @@ -280,7 +281,9 @@ static int cr_may_checkpoint_task(struct task_struct *t, struct cr_ctx *ctx)
>  	if (!ptrace_may_access(t, PTRACE_MODE_READ))
>  		return -EPERM;
> 
> -	/* FIXME: verify that the task is frozen (unless self) */
> +	/* verify that the task is frozen (unless self) */
> +	if (t != current && !frozen(t))
> +		return -EBUSY;
> 
>  	/* FIXME: change this for nested containers */
>  	if (task_nsproxy(t) != ctx->root_nsproxy)
> -- 
> 1.5.2.5