Re: 2.4+ptrace exploit fix breaks root's ability to strace

[Arjan van de Ven <arjanv@redhat.com>]

On Sat, Mar 22, 2003 at 05:13:12PM +0000, Russell King wrote:
> 
> int ptrace_check_attach(struct task_struct *child, int kill)
> {
> 	...
> +       if (!is_dumpable(child))
> +               return -EPERM;
> }
> 
> So, we went from being able to ptrace daemons as root, to being able to
> attach daemons and then being unable to do anything with them, even if
> you're root (or have the CAP_SYS_PTRACE capability).  I think this
> behaviour is getting on for being described as "insane" 8) and is
> clearly wrong.

ok it seems this check is too strong. It *has* to check
child->task_dumpable and return -EPERM, but child->mm->dumpable is not
needed.