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

Tony Jones
2005-08-26T17:36:21Z

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