svn commit: r348843 - head/sys/vm

[Shawn Webb]

Sounds good! I think the manpage still might still need a change
to match the current behavior, or perhaps matching something similar
to that vm_mmap.c comment. But that comment brings another question:
what's the definition of "old binaries"? a.out?

Thanks,

-- 
Shawn Webb
Cofounder / Security Engineer
HardenedBSD

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On Mon, Jun 10, 2019 at 09:19:55AM -0500, Doug Moore wrote:
> This comment appears in vm_mmap.c:
> 
> ???? * Mapping of length 0 is only allowed for old binaries.
> 
> and my intent was to say, to whoever wrote that comment, that I was not
> disallowing the mapping of length zero with this change.? I was only
> intending to affect a case in which the length was transformed to zero,
> and which was the problem that Peter Holm reported.
> 
> Doug Moore
> 
> On 6/10/19 8:00 AM, Shawn Webb wrote:
> > On Mon, Jun 10, 2019 at 03:07:11AM +0000, Doug Moore wrote:
> >> Author: dougm
> >> Date: Mon Jun 10 03:07:10 2019
> >> New Revision: 348843
> >> URL: https://svnweb.freebsd.org/changeset/base/348843
> >>
> >> Log:
> >>   There are times when a len==0 parameter to mmap is okay. But on a
> >>   32-bit machine, a len parameter just a few bytes short of 4G, rounded
> >>   up to a page boundary and hitting zero then, is not okay. Return
> >>   failure in that case.
> >>   
> >>   Reported by: pho
> >>   Reviewed by: alc, kib (mentor)
> >>   Tested by: pho
> >>   Differential Revision: https://reviews.freebsd.org/D20580
> >>
> >> Modified:
> >>   head/sys/vm/vm_mmap.c
> >>
> >> Modified: head/sys/vm/vm_mmap.c
> >> ==============================================================================
> >> --- head/sys/vm/vm_mmap.c	Sun Jun  9 22:55:21 2019	(r348842)
> >> +++ head/sys/vm/vm_mmap.c	Mon Jun 10 03:07:10 2019	(r348843)
> >> @@ -257,7 +257,10 @@ kern_mmap(struct thread *td, uintptr_t addr0, size_t s
> >>  
> >>  	/* Adjust size for rounding (on both ends). */
> >>  	size += pageoff;			/* low end... */
> >> -	size = (vm_size_t) round_page(size);	/* hi end */
> >> +	/* Check for rounding up to zero. */
> >> +	if (round_page(size) < size)
> >> +		return (EINVAL);
> > The mmap(2) manpage says that len==0 results in EINVAL, so the manpage
> > needs updating.
> >
> > I'm curious what "there are times" refers to. Can you or the original
> > reporter elaborate those cases?
> >
> > Thanks a lot!
> >
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