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From: Michal Hocko <mhocko@kernel.org>
To: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
	Joel Stanley <joel@jms.id.au>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux-Next Mailing List <linux-next@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Abdul Haleem <abdhalee@linux.vnet.ibm.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	"James E.J. Bottomley" <jejb@parisc-linux.org>,
	Helge Deller <deller@gmx.de>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	"David S. Miller" <davem@davemloft.net>,
	Chris Zankel <chris@zankel.net>,
	Max Filippov <jcmvbkbc@gmail.com>,
	linux-arm-kernel@lists.infradead.org, linuxppc-dev@lis
Subject: Re: linux-next: Tree for Nov 7
Date: Tue, 14 Nov 2017 08:07:48 +0100
Message-ID: <20171114070748.in5zdc4giqbxowjy@dhcp22.suse.cz> (raw)
In-Reply-To: <c52fa249-9583-18a2-cbac-28abfb23d5a5@oracle.com>

On Mon 13-11-17 09:35:22, Khalid Aziz wrote:
> On 11/13/2017 09:06 AM, Michal Hocko wrote:
> > OK, so this one should take care of the backward compatibility while
> > still not touching the arch code
> > ---
> > commit 39ff9bf8597e79a032da0954aea1f0d77d137765
> > Author: Michal Hocko <mhocko@suse.com>
> > Date:   Mon Nov 13 17:06:24 2017 +0100
> > 
> >      mm: introduce MAP_FIXED_SAFE
> >      MAP_FIXED is used quite often but it is inherently dangerous because it
> >      unmaps an existing mapping covered by the requested range. While this
> >      might be might be really desidered behavior in many cases there are
> >      others which would rather see a failure than a silent memory corruption.
> >      Introduce a new MAP_FIXED_SAFE flag for mmap to achive this behavior.
> >      It is a MAP_FIXED extension with a single exception that it fails with
> >      ENOMEM if the requested address is already covered by an existing
> >      mapping. We still do rely on get_unmaped_area to handle all the arch
> >      specific MAP_FIXED treatment and check for a conflicting vma after it
> >      returns.
> >      Signed-off-by: Michal Hocko <mhocko@suse.com>
> > 
> > ...... deleted .......
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 680506faceae..aad8d37f0205 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -1358,6 +1358,10 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
> >   	if (mm->map_count > sysctl_max_map_count)
> >   		return -ENOMEM;
> > +	/* force arch specific MAP_FIXED handling in get_unmapped_area */
> > +	if (flags & MAP_FIXED_SAFE)
> > +		flags |= MAP_FIXED;
> > +
> >   	/* Obtain the address to map to. we verify (or select) it and ensure
> >   	 * that it represents a valid section of the address space.
> >   	 */
> 
> Do you need to move this code above:
> 
>         if (!(flags & MAP_FIXED))
>                 addr = round_hint_to_min(addr);
> 
>         /* Careful about overflows.. */
>         len = PAGE_ALIGN(len);
>         if (!len)
>                 return -ENOMEM;
> 
> Not doing that might mean the hint address will end up being rounded for
> MAP_FIXED_SAFE which would change the behavior from MAP_FIXED.

Yes, I will move it.
-- 
Michal Hocko
SUSE Labs

  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-07  5:22 Stephen Rothwell
2017-11-07 22:22 ` Joel Stanley
2017-11-08 14:20   ` Michal Hocko
2017-11-10 12:30     ` Michal Hocko
2017-11-12  1:08       ` Joel Stanley
2017-11-13  9:20         ` Michal Hocko
2017-11-13  9:34           ` Russell King - ARM Linux
2017-11-13  9:42           ` Michal Hocko
2017-11-13 11:34             ` Michael Ellerman
2017-11-13 12:00               ` Michal Hocko
2017-11-13 15:16                 ` Michal Hocko
2017-11-13 15:48                   ` Russell King - ARM Linux
2017-11-13 15:59                     ` Michal Hocko
2017-11-13 15:49                   ` Michal Hocko
2017-11-13 16:06                     ` Michal Hocko
2017-11-13 16:35                       ` Khalid Aziz
2017-11-14  7:07                         ` Michal Hocko [this message]
2017-11-14  9:18                       ` Michael Ellerman
2017-11-14  9:29                         ` Michal Hocko
2017-11-14  9:02                   ` Michael Ellerman
2017-11-14  8:54                 ` Michael Ellerman
2017-11-14  9:04                   ` Michal Hocko
2017-11-14 14:52                     ` Khalid Aziz
2017-11-13 14:11           ` Michal Hocko
2017-11-13 15:09             ` Russell King - ARM Linux
2017-11-13 15:31               ` Michal Hocko
2017-11-14  0:03         ` Andrew Morton
2017-11-14  0:36           ` Stephen Rothwell
  -- strict thread matches above, loose matches on Subject: below --
2019-11-07  8:07 Stephen Rothwell
2018-11-07  3:16 Stephen Rothwell
2013-11-07  7:31 Stephen Rothwell
2012-11-07  5:15 Stephen Rothwell

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