Re: [PATCH 2/2] execve: check the VM has enough memory at first

[KOSAKI Motohiro <kosaki.motohiro () jp fujitsu com>]

> > On Wed, Sep 8, 2010 at 10:04 PM, KOSAKI Motohiro
> > <kosaki.motohiro () jp fujitsu com> wrote:
> > > After this patch, execve() expand stack at first and receive to
> > > check vm_enough_memory() properly. then, too long argument of
> > > execve() than the machine memory return EFAULT properly.
> >
> > This is horrible. We don't want to walk the arguments one more time
> > just for this. Let's just improve the checks that we do as we go
> > along.
> >
> >                             Linus
>
> Okey. I'll consider new way in this night.

After while thinking, I decided to just drop this idea. because
 1) If one pass check is must, we can't reuse vm-overcommit check.
 2) Glibc has the duplicated hueristic, then we can't change it nor
    introduce new hard limit. (Sh*t)
 3) This is not must fix, it only mitigate a pain when accidental large
    argv case. Only OOM fixes enough care intended attack case.
 4) distro can change default of rlim_max of RLIMIT_STACK. It protect
    from RLIM_INFINITY smash.

Briefly says, to introduce new limit has bad benefit/risk balance. Sadly.