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From: Michal Hocko <mhocko@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-api@vger.kernel.org, Khalid Aziz <khalid.aziz@oracle.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	Andrea Arcangeli <aarcange@redhat.com>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	linux-arch@vger.kernel.org, Florian Weimer <fweimer@redhat.com>,
	John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH 1/2] mm: introduce MAP_FIXED_SAFE
Date: Wed, 13 Dec 2017 14:01:35 +0100
Message-ID: <20171213130135.GG25185@dhcp22.suse.cz> (raw)
In-Reply-To: <20171213125053.GB2384@bombadil.infradead.org>

On Wed 13-12-17 04:50:53, Matthew Wilcox wrote:
> On Wed, Dec 13, 2017 at 10:25:49AM +0100, Michal Hocko wrote:
> > +++ b/mm/mmap.c
> > @@ -1342,6 +1342,10 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
> >  		if (!(file && path_noexec(&file->f_path)))
> >  			prot |= PROT_EXEC;
> >  
> > +	/* force arch specific MAP_FIXED handling in get_unmapped_area */
> > +	if (flags & MAP_FIXED_SAFE)
> > +		flags |= MAP_FIXED;
> > +
> >  	if (!(flags & MAP_FIXED))
> >  		addr = round_hint_to_min(addr);
> >  
> 
> We're up to 22 MAP_ flags now.  We'll run out soon.  Let's preserve half
> of a flag by giving userspace the definition:
> 
> #define MAP_FIXED_SAFE	(MAP_FIXED | _MAP_NOT_HINT)

I've already tried to explain why this cannot be a modifier for
MAP_FIXED. Read about the backward compatibility note...
Or do I misunderstand what you are saying here?
 
> then in here:
> 
> 	if ((flags & _MAP_NOT_HINT) && !(flags & MAP_FIXED))
> 		return -EINVAL;
> 
> Now we can use _MAP_NOT_HINT all by itself in the future to mean
> something else.

-- 
Michal Hocko
SUSE Labs

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Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-13  9:25 [PATCH v2 0/2] " Michal Hocko
2017-12-13  9:25 ` [PATCH 1/2] " Michal Hocko
     [not found]   ` <20171213092550.2774-2-mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2017-12-13 12:50     ` Matthew Wilcox
2017-12-13 13:01       ` Michal Hocko [this message]
2017-12-13  9:25 ` [PATCH 2/2] fs, elf: drop MAP_FIXED usage from elf_map Michal Hocko
2017-12-16  0:49   ` [2/2] " Andrei Vagin
2017-12-18  9:13     ` Michal Hocko
2017-12-18 18:12       ` Andrei Vagin
2017-12-13  9:31 ` [PATCH 1/2] mmap.2: document new MAP_FIXED_SAFE flag Michal Hocko
2017-12-13  9:31   ` [PATCH 2/2] mmap.2: MAP_FIXED updated documentation Michal Hocko
2017-12-13 12:55     ` Pavel Machek
2017-12-13 13:03       ` Cyril Hrubis
2017-12-13 13:04       ` Michal Hocko
2017-12-13 13:09         ` Pavel Machek
2017-12-13 13:16           ` Michal Hocko
     [not found]             ` <20171213131640.GJ25185-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2017-12-13 13:21               ` Pavel Machek
2017-12-13 13:35                 ` Michal Hocko
2017-12-13 14:40                 ` Cyril Hrubis
2017-12-13 23:19                   ` Kees Cook
     [not found]                     ` <CAGXu5jLqE6cUxk-Girx6PG7upEzz8jmu1OH_3LVC26iJc2vTxQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-14  7:07                       ` Michal Hocko
2017-12-18 19:12                     ` Michael Kerrisk (man-pages)
2017-12-18 20:19                       ` Kees Cook
2017-12-18 20:33                         ` Matthew Wilcox
     [not found]                         ` <CAGXu5jJ289R9koVoHmxcvUWr6XHSZR2p0qq3WtpNyN-iNSvrNQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-21 12:38                           ` Michael Ellerman
2017-12-21 14:59                             ` known bad patch in -mm tree was " Pavel Machek
2017-12-21 15:08                               ` Michal Hocko
2017-12-21 22:24                             ` Andrew Morton
2017-12-22  0:06                               ` Michael Ellerman
2017-12-14  2:52     ` Jann Horn
     [not found]       ` <CAG48ez0JZ3PVW3vgSXDmDijS+a_5bSX9qNuyggnsB6JTSkKngA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-14  5:28         ` John Hubbard
2017-12-14 23:06       ` John Hubbard
     [not found]         ` <b4fb7b3a-e53e-bf87-53c5-186751a14f4e-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2017-12-14 23:10           ` Jann Horn
     [not found] ` <20171213092550.2774-1-mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2017-12-13 12:25   ` [PATCH v2 0/2] mm: introduce MAP_FIXED_SAFE Matthew Wilcox
2017-12-13 12:34     ` Michal Hocko
2017-12-13 17:13   ` Kees Cook
2017-12-15  9:02     ` Michael Ellerman
2017-12-14  0:32   ` Andrew Morton
2017-12-14  1:35     ` David Goldblatt
2017-12-14  1:42       ` David Goldblatt
2017-12-14 12:44     ` Edward Napierala
2017-12-14 13:15       ` Michal Hocko
2017-12-14 14:54         ` Edward Napierala
2017-12-19 12:40           ` David Laight
2017-12-19 12:46             ` Michal Hocko
  -- strict thread matches above, loose matches on Subject: below --
2017-11-29 14:42 [PATCH " Michal Hocko
2017-11-29 14:42 ` [PATCH 1/2] " Michal Hocko
2017-12-06  5:15   ` Michael Ellerman
2017-12-06  9:27     ` Michal Hocko
2017-12-06 10:02       ` Michal Hocko
2017-12-07 12:07   ` Pavel Machek

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