Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec

James Morris
2011-02-08T03:43:23Z

On Mon, 7 Feb 2011, Kees Cook wrote:

> Sure, I know about O_CLOEXEC, but this is about protecting the
> just-been-execed setuid process from the attacking process that has no
> reason to set O_CLOEXEC.
>
> Something like this needs to be enforced on the kernel side. I.e. these
> file in /proc need to have O_CLOEXEC set in a way that cannot be unset.
>
> > Changing the behavior in the core kernel will break userspace.
>
> I don't think /proc/$pid/* needs to stay open across execs, does it? Or at
> least the non-0444 files should be handled separately.

Actually, this seems like a more general kind of bug in proc rather than a
leaked fd. Each child task should only see its own /proc/[pid] data.

- James
--
James Morris
<jmorris@namei.org>