Re: [patch 0/4] MAP_NOZERO v2 - VM_NOZERO/MAP_NOZERO early summer madness

Davide Libenzi
2007-07-02T22:39:08Z

On Mon, 2 Jul 2007, Andy Isaacson wrote:

> On Sat, Jun 30, 2007 at 12:03:07PM -0700, Davide Libenzi wrote:
> > I think the focus should be to find a case where under the currently
> > implemented policy for MAP_NOZERO, MAP_NOZERO represent a loss of security
> > WRT no MAP_NOZERO. I have not been able to find one yet, although Andy
> > found a potential one in the setuid+exec/ptrace race (fixed by a patch
> > that should IMO go in in any case).
>
> BTW, the ptrace variant of this issue is not a problem -- PTRACE_ATTACH
> running as newuid gets EPERM when trying to attach at /* here */ below.
>
> setuid(newuid);
> /* here */
> exec(...);
> exit(1);
>
> sys_setuid sets current->mm->dumpable = suid_dumpable, so unless the
> admin asked for it, there is no risk WRT PTRACE_ATTACH. However, this
> risk vector does need to be considered when implementing MAP_NOZERO.

Yes, I missed that. Ptrace is fine there. The 3 lines patch is still
needed for MAP_NOZERO though.

- Davide