Re: [PATCH 2/2] mmap.2: MAP_FIXED updated documentation

From: Michal Hocko <mhocko@kernel.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>,
	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>,
	Matthew Wilcox <willy@infradead.org>,
	Jann Horn <jannh@google.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Cyril Hrubis <chrubis@suse.cz>
Subject: Re: [PATCH 2/2] mmap.2: MAP_FIXED updated documentation
Date: Wed, 13 Dec 2017 14:35:47 +0100	[thread overview]
Message-ID: <20171213133547.GK25185@dhcp22.suse.cz> (raw)
In-Reply-To: <20171213132105.GA20517@amd>

On Wed 13-12-17 14:21:05, Pavel Machek wrote:
> On Wed 2017-12-13 14:16:40, Michal Hocko wrote:
> > On Wed 13-12-17 14:09:00, Pavel Machek wrote:
> > > On Wed 2017-12-13 14:04:58, Michal Hocko wrote:
> > > > On Wed 13-12-17 13:55:40, Pavel Machek wrote:
> > > > > On Wed 2017-12-13 10:31:10, Michal Hocko wrote:
> > > > > > From: John Hubbard <jhubbard@nvidia.com>
> > > > > > 
> > > > > >     -- Expand the documentation to discuss the hazards in
> > > > > >        enough detail to allow avoiding them.
> > > > > > 
> > > > > >     -- Mention the upcoming MAP_FIXED_SAFE flag.
> > > > > 
> > > > > Pretty map everyone agreed MAP_FIXED_SAFE was a bad
> > > > > name. MAP_FIXED_NOREPLACE (IIRC) was best replacement.
> > > > 
> > > > Please read http://lkml.kernel.org/r/20171213092550.2774-1-mhocko@kernel.org
> > > 
> > > Please fix your patches according to the feedback...
> > > 
> > > NACCKED-by: Pavel Machek <pavel@ucw.cz>
> > 
> > Good luck pursuing this further then. I am not going to spend time on
> > naming bikeheds. I have more pressing stuff to work on.
> 
> You selected stupid name for a flag. Everyone and their dog agrees
> with that.

Not sure about your dog but mine says that a flag which fixes an
_unsafe_ aspects of MAP_FIXED can be called MAP_FIXED_SAFE just fine.

Anyway, I am not going to argue about this further. I've implemented the
code, gathered uscases and fortified an in-kernel user which already led
to a security issue in the past. I consider my part done here. I do not
agree that MAP_FIXED_NOREPLACE would be so much better to respin and
then deal with what about this MAP_$FOO. If there are really stong
feelings about this then feel free to take these patches, do
s@MAP_FIXED_SAFE@MAP_$FOO@ and try to upstream them yourself.
-- 
Michal Hocko
SUSE Labs

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