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From: Mike Kravetz <mike.kravetz@oracle.com>
To: linux-mm@kvack.org, Linux API <linux-api@vger.kernel.org>,
	linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Michal Hocko <mhocko@suse.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>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: [PATCH v2] mm/mremap: Fail map duplication attempts for private mappings
Date: Thu, 20 Jul 2017 13:37:59 -0700	[thread overview]
Message-ID: <1500583079-26504-1-git-send-email-mike.kravetz@oracle.com> (raw)
In-Reply-To: <20170720082058.GF9058@dhcp22.suse.cz>

mremap will create a 'duplicate' mapping if old_size == 0 is
specified.  Such duplicate mappings make no sense for private
mappings.  If duplication is attempted for a private mapping,
mremap creates a separate private mapping unrelated to the
original mapping and makes no modifications to the original.
This is contrary to the purpose of mremap which should return
a mapping which is in some way related to the original.

Therefore, return EINVAL in the case where if 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>
---
 mm/mremap.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/mremap.c b/mm/mremap.c
index cd8a1b1..949f6a7 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -383,6 +383,15 @@ 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 a mapping is 'duplicated'.
+	 * Do not allow this for private mappings.
+	 */
+	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

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  reply	other threads:[~2017-07-20 20:37 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         ` Mike Kravetz [this message]
2017-07-21 14:36           ` [PATCH v2] " 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

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