From: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Mike Kravetz <mike.kravetz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Andrea Arcangeli
<aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Aaron Lu <aaron.lu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
"Kirill A . Shutemov"
<kirill.shutemov-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>,
Anshuman Khandual
<khandual-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: Re: [PATCH v2] mm/mremap: Fail map duplication attempts for private mappings
Date: Mon, 24 Jul 2017 10:50:46 +0200 [thread overview]
Message-ID: <20170724085045.GD25221@dhcp22.suse.cz> (raw)
In-Reply-To: <cb9d9f6a-7095-582f-15a5-62643d65c736-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
On Fri 21-07-17 14:18:31, Mike Kravetz wrote:
[...]
> >From 5c4a1602bd6a942544ed011dc0a72fd258e874b2 Mon Sep 17 00:00:00 2001
> From: Mike Kravetz <mike.kravetz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Date: Wed, 12 Jul 2017 13:52:47 -0700
> Subject: [PATCH] mm/mremap: Fail map duplication attempts for private mappings
>
> mremap will attempt to create a 'duplicate' mapping if old_size
> == 0 is specified. In the case of private mappings, mremap
> will actually create a fresh separate private mapping unrelated
> to the original. This does not fit with the design semantics of
> mremap as the intention is to create a new mapping based on the
> original.
>
> Therefore, return EINVAL in the case where an attempt is made
> to duplicate a private mapping. Also, print a warning message
> (once) if such an attempt is made.
>
> Signed-off-by: Mike Kravetz <mike.kravetz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>
Thanks!
> ---
> mm/mremap.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/mm/mremap.c b/mm/mremap.c
> index cd8a1b1..75b167d 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -383,6 +383,19 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
> if (!vma || vma->vm_start > addr)
> return ERR_PTR(-EFAULT);
>
> + /*
> + * !old_len is a special case where an attempt is made to 'duplicate'
> + * a mapping. This makes no sense for private mappings as it will
> + * instead create a fresh/new mapping unrelated to the original. This
> + * is contrary to the basic idea of mremap which creates new mappings
> + * based on the original. There are no known use cases for this
> + * behavior. As a result, fail such attempts.
> + */
> + if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
> + pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
> + return ERR_PTR(-EINVAL);
> + }
> +
> if (is_vm_hugetlb_page(vma))
> return ERR_PTR(-EINVAL);
>
> --
> 2.7.5
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2017-07-24 8:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1499961495-8063-1-git-send-email-mike.kravetz@oracle.com>
[not found] ` <1499961495-8063-1-git-send-email-mike.kravetz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
2017-07-13 19:11 ` [PATCH] mm/mremap: Fail map duplication attempts for private mappings Vlastimil Babka
2017-07-13 22:33 ` Mike Kravetz
2017-07-14 4:51 ` Anshuman Khandual
[not found] ` <415625d2-1be9-71f0-ca11-a014cef98a3f-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
2017-07-14 8:26 ` Michal Hocko
2017-07-14 17:29 ` Mike Kravetz
2017-07-17 6:44 ` Michal Hocko
2017-07-19 16:39 ` Mike Kravetz
2017-07-20 8:20 ` Michal Hocko
2017-07-20 20:37 ` [PATCH v2] " Mike Kravetz
2017-07-21 14:36 ` Michal Hocko
2017-07-21 21:18 ` Mike Kravetz
[not found] ` <cb9d9f6a-7095-582f-15a5-62643d65c736-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
2017-07-24 8:50 ` Michal Hocko [this message]
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