From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: Rik van Riel <riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
mike.kravetz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
fweimer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
colm-ZXBCfW2eEe/k1uMJSBkQmQ@public.gmane.org,
keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org,
luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org,
wad-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org,
mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org,
dave.hansen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org
Subject: Re: [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK
Date: Fri, 18 Aug 2017 11:15:45 -0700 [thread overview]
Message-ID: <20170818111545.ab371cfedb71d13d76590030@linux-foundation.org> (raw)
In-Reply-To: <1503073709.6577.68.camel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
On Fri, 18 Aug 2017 12:28:29 -0400 Rik van Riel <riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> On Thu, 2017-08-17 at 15:50 -0700, Andrew Morton wrote:
> > On Tue, 15 Aug 2017 22:18:19 -0400 Rik van Riel <riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > wrote:
> >
> > > > > --- a/mm/madvise.c
> > > > > +++ b/mm/madvise.c
> > > > > @@ -80,6 +80,17 @@ static long madvise_behavior(struct
> > > > > vm_area_struct *vma,
> > > > > __ }
> > > > > __ new_flags &= ~VM_DONTCOPY;
> > > > > __ break;
> > > > > + case MADV_WIPEONFORK:
> > > > > + /* MADV_WIPEONFORK is only supported on
> > > > > anonymous
> > > > > memory. */
> > > > > + if (vma->vm_file || vma->vm_flags & VM_SHARED)
> > > > > {
> > > > > + error = -EINVAL;
> > > > > + goto out;
> > > > > + }
> > > > > + new_flags |= VM_WIPEONFORK;
> > > > > + break;
> > > > > + case MADV_KEEPONFORK:
> > > > > + new_flags &= ~VM_WIPEONFORK;
> > > > > + break;
> > > > > __ case MADV_DONTDUMP:
> > > > > __ new_flags |= VM_DONTDUMP;
> > > > > __ break;
> > > >
> > > > It seems odd to permit MADV_KEEPONFORK against other-than-anon
> > > > vmas?
> > >
> > > Given that the only way to set VM_WIPEONFORK is through
> > > MADV_WIPEONFORK, calling MADV_KEEPONFORK on an
> > > other-than-anon vma would be equivalent to a noop.
> > >
> > > If new_flags == vma->vm_flags, madvise_behavior() will
> > > immediately exit.
> >
> > Yes, but calling MADV_WIPEONFORK against an other-than-anon vma is
> > presumably a userspace bug.____A bug which will probably result in
> > userspace having WIPEONFORK memory which it didn't want.____The kernel
> > can trivially tell userspace that it has this bug so why not do so?
>
> Uh, what?
>
Braino. I meant MADV_KEEPONFORK. Calling MADV_KEEPONFORK against an
other-than-anon vma is a presumptive userspace bug and the kernel
should report that.
next prev parent reply other threads:[~2017-08-18 18:15 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-11 21:28 [PATCH v4 0/2] mm,fork,security: introduce MADV_WIPEONFORK riel-H+wXaHxf7aLQT0dZR+AlfA
2017-08-11 21:28 ` [PATCH 1/2] x86,mpx: make mpx depend on x86-64 to free up VMA flag riel
2017-08-11 21:28 ` [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK riel
2017-08-15 22:51 ` Andrew Morton
2017-08-16 2:18 ` Rik van Riel
2017-08-17 22:50 ` Andrew Morton
2017-08-18 16:28 ` Rik van Riel
[not found] ` <1503073709.6577.68.camel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-08-18 18:15 ` Andrew Morton [this message]
[not found] ` <20170818111545.ab371cfedb71d13d76590030-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2017-08-19 0:02 ` Rik van Riel
2017-08-18 17:25 ` Mike Kravetz
-- strict thread matches above, loose matches on Subject: below --
2017-08-11 19:19 [PATCH v3 0/2] mm,fork,security: " riel-H+wXaHxf7aLQT0dZR+AlfA
2017-08-11 19:19 ` [PATCH 2/2] mm,fork: " riel
[not found] ` <20170811191942.17487-3-riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-08-11 19:42 ` Linus Torvalds
[not found] ` <CA+55aFzA+7CeCdUi-13DfOeE3FfhtTPMMmBA4UQx8FixXiD4YA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-11 20:27 ` Rik van Riel
2017-08-11 20:50 ` Linus Torvalds
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