Re: [PATCH 2/5] Rework stubs in security.h

[Tony Jones]

On Wed, Aug 24, 2005 at 06:20:30PM -0700, Chris Wright wrote:

>  static inline int security_ptrace (struct task_struct * parent, struct task_struct * child)
>  {
> +#ifdef CONFIG_SECURITY
>  	return security_ops->ptrace (parent, child);
> +#else
> +	return cap_ptrace (parent, child);
> +#endif
> +
>  }

The discussion about composing with commoncap made me think about whether
this is the best way to do this.   It seems that we're heading towards a
requirement that every module internally compose with commoncap.  

If so (apart from the obvious correctness issues when they don't) it's work
for each module and composing N of them under stacker obviously creates 
overhead.

Would the following not be a better approach?

static inline int security_ptrace (struct task_struct * parent, struct task_struct * child)
{
int ret;
	ret=cap_ptrace (parent, child);
#ifdef CONFIG_SECURITY
	if (!ret && security_ops->ptrace)
		ret=security_ops->ptrace(parent, child);
#endif
	return ret;
}

If every module is already internally composing, there shouldn't be a 
performance cost for the additional branch inside the #ifdef.

I havn't looked at every single hook and it's users to see if this would
cause a problem.  I noticed SELinux calls sec->capget() post rather than pre 
it's processing which may be an issue.

Tony
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