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Date:      Fri, 2 Mar 2018 17:59:13 +0000
From:      Brooks Davis <brooks@freebsd.org>
To:        Pedro Giffuni <pfg@FreeBSD.org>
Cc:        Konstantin Belousov <kib@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org, Eitan Adler <lists@eitanadler.com>
Subject:   Re: svn commit: r330285 - head/sys/sys
Message-ID:  <20180302175913.GA68675@spindle.one-eyed-alien.net>
In-Reply-To: <dba3b880-58d0-e6df-8f99-4d27919134c9@FreeBSD.org>
References:  <201803021647.w22Gl2t7092316@repo.freebsd.org> <dba3b880-58d0-e6df-8f99-4d27919134c9@FreeBSD.org>

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On Fri, Mar 02, 2018 at 12:43:34PM -0500, Pedro Giffuni wrote:
> (cc in Eitan as he may be interested in the extra restrict cases)
>=20
>=20
> On 02/03/2018 11:47, Konstantin Belousov wrote:
> > Author: kib
> > Date: Fri Mar  2 16:47:02 2018
> > New Revision: 330285
> > URL: https://svnweb.freebsd.org/changeset/base/330285
> >
> > Log:
> >    Remove _Nonnull attributes from user addresses arguments for
> >    copyout(9) family.
> >   =20
> >    The addresses are user-controllable, and if the process ABI allows
> >    mapping at zero, then the zero address is meaningful, contradicting
> >    the definition of _Nonnull.  In any case, it does not require any
> >    special code to handle NULL udaddr.
> >   =20
>=20
> FWIW, the _Nonnull attributes didn't do much at all beyond producing a=20
> warning.
> They replaced the GNU __nonnull() attributes which were much more dangero=
us.
> I am OK with seeing both gone here though.

Even if the process ABI doesn't allow mapping at NULL, we have code that
depends on copyout(NULL, foo, 0) being a nop.

-- Brooks

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