From: Michal Hocko <mhocko@kernel.org>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, Linux API <linux-api@vger.kernel.org>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Aaron Lu <aaron.lu@intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Anshuman Khandual <khandual@linux.vnet.ibm.com>
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@oracle.com>
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@oracle.com>
> 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@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
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
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prev parent reply other threads:[~2017-07-24 8:50 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-13 15:58 [PATCH] mm/mremap: Fail map duplication attempts for private mappings Mike Kravetz
2017-07-13 19:11 ` Vlastimil Babka
2017-07-13 22:33 ` Mike Kravetz
2017-07-14 4:51 ` Anshuman Khandual
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
2017-07-24 8:50 ` Michal Hocko [this message]
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