From: Khalid Aziz <khalid.aziz@oracle•com>
To: Michal Hocko <mhocko@kernel•org>, Michael Ellerman <mpe@ellerman•id.au>
Cc: 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@lists•ozlabs.org, linux-mips@linux-mips•org
Subject: Re: linux-next: Tree for Nov 7
Date: Mon, 13 Nov 2017 09:35:22 -0700 [thread overview]
Message-ID: <c52fa249-9583-18a2-cbac-28abfb23d5a5@oracle.com> (raw)
In-Reply-To: <20171113160637.jhekbdyfpccme3be@dhcp22.suse.cz>
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.
--
Khalid
next prev parent reply other threads:[~2017-11-13 16:35 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-07 5:22 linux-next: Tree for Nov 7 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 [this message]
2017-11-14 7:07 ` Michal Hocko
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 --
2025-11-07 4:32 Stephen Rothwell
2024-11-07 12:19 Stephen Rothwell
2023-11-07 1:17 Stephen Rothwell
2022-11-07 3:44 Stephen Rothwell
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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