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Date:      Mon, 10 Jun 2019 11:39:14 -0400
From:      Shawn Webb <shawn.webb@hardenedbsd.org>
To:        Bruce Evans <brde@optusnet.com.au>
Cc:        Doug Moore <dougm@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org, pho@freebsd.org
Subject:   Re: svn commit: r348843 - head/sys/vm
Message-ID:  <20190610153914.o2n5yjgfu3ubzbbt@mutt-hbsd>
In-Reply-To: <20190611010531.A3253@besplex.bde.org>
References:  <201906100307.x5A37BFt099669@repo.freebsd.org> <20190610130034.k2nzitvaxvpj5lzx@mutt-hbsd> <20190611010531.A3253@besplex.bde.org>

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On Tue, Jun 11, 2019 at 01:33:23AM +1000, Bruce Evans wrote:
> On Mon, 10 Jun 2019, Shawn Webb wrote:
>=20
> > On Mon, Jun 10, 2019 at 03:07:11AM +0000, Doug Moore wrote:
> > > ...
> > > Log:
> > >   There are times when a len=3D=3D0 parameter to mmap is okay. But on=
 a
> > >   32-bit machine, a len parameter just a few bytes short of 4G, round=
ed
> > >   up to a page boundary and hitting zero then, is not okay. Return
> > >   failure in that case.
> > > ...
> > >  	/* Adjust size for rounding (on both ends). */
> > >  	size +=3D pageoff;			/* low end... */
> > > -	size =3D (vm_size_t) round_page(size);	/* hi end */
> > > +	/* Check for rounding up to zero. */
> > > +	if (round_page(size) < size)
> > > +		return (EINVAL);
> >=20
> > The mmap(2) manpage says that len=3D=3D0 results in EINVAL, so the manp=
age
> > needs updating.
>=20
> The man page doesn't say that only len =3D=3D 0 results in EINVAL, so it =
is
> not incorrect.

https://github.com/freebsd/freebsd/blob/master/lib/libc/sys/mmap.2#L451-L455

Tons of error conditions listed, one of which is len=3D=3D0.

Thanks,

--=20
Shawn Webb
Cofounder / Security Engineer
HardenedBSD

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