svn commit: r348843 - head/sys/vm

[Brooks Davis]

On Mon, Jun 10, 2019 at 09:00:34AM -0400, 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.

The manpage is correct for ABIs people are actually writing code for
(ELF).  I suppose it could document the exception for a.out (see the
conditional containing SV_CURPROC_FLAG(SV_AOUT) in kern_mmap()), but it
should be in BUGS, HISTORY, or some such.

-- Brooks
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