Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree

Cyrill Gorcunov
2012-02-15T19:56:19Z

On Wed, Feb 15, 2012 at 07:43:36PM +0100, Oleg Nesterov wrote:
...
>
> Cough... this is question I am trying to ask ;)
>
> Let me try again. To simplify, lets discuss the KCMP_VM case
> only.
>
> I do not really understand why do we need ptrace_may_access().
> I do not see any security problems with kcmp_ptr(task->mm), but
> I am not expert.
>
> However, you added this check so I assume you have some reason.
> But this can race with execve(setuid_app) and KCMP_VM can play
> with task->mm after this task raises its caps. If this is fine,
> then why do we need ptrace_may_access?
>

This makes me scratch the head ;) I think ptrace_may_access (or
some other security test) should remain since it's somehow weird
if non-root task will be able to find objects order from privileged
task. Thus I need to find a way how to handle execve(setuid_app).
Need to think...

Cyrill