Re: [PATCH v3] seccomp: add ptrace options for suspend/resume

[Oleg Nesterov <oleg@redhat.com>]

Tycho,

I hate myself, but I have another nit ;) again, it is not that I think
you should updtate the patch, just fyi...

On 06/05, Tycho Andersen wrote:
>
> --- a/include/linux/seccomp.h
> +++ b/include/linux/seccomp.h
> @@ -95,4 +95,14 @@ static inline void get_seccomp_filter(struct task_struct *tsk)
>  	return;
>  }
>  #endif /* CONFIG_SECCOMP_FILTER */
> +
> +#ifdef CONFIG_CHECKPOINT_RESTORE
> +extern bool may_suspend_seccomp(void);
> +#else
> +static inline bool may_suspend_seccomp(void)
> +{
> +	return false;
> +}
> +#endif

This looks wrong. There is no "extern may_suspend_seccomp()" if
CONFIG_SECCOMP=n, kernel/seccomp.c is not compiled. So you need another
ifdef(CONFIG_SECCOMP).

At the same time this does not matter and you do not need the dummy
"inline" version at all:

> @@ -556,6 +557,15 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data)
>  	if (data & ~(unsigned long)PTRACE_O_MASK)
>  		return -EINVAL;
>  
> +	if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
> +		if (!config_enabled(CONFIG_CHECKPOINT_RESTORE) ||
> +		    !config_enabled(CONFIG_SECCOMP))
> +			return -EINVAL;
> +
> +		if (!may_suspend_seccomp())
> +			return -EPERM;

gcc will optimize out may_suspend_seccomp() unless both options are
enabled.

Oleg.