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* [PATCH] mm/mremap: Fail map duplication attempts for private mappings
@ 2017-07-13 15:58 Mike Kravetz
  2017-07-13 19:11 ` Vlastimil Babka
  0 siblings, 1 reply; 13+ messages in thread
From: Mike Kravetz @ 2017-07-13 15:58 UTC (permalink / raw)
  To: linux-mm, linux-kernel
  Cc: Andrew Morton, Andrea Arcangeli, Michal Hocko, Aaron Lu,
	Kirill A . Shutemov, Vlastimil Babka, Anshuman Khandual,
	Mike Kravetz

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.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/mremap.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/mremap.c b/mm/mremap.c
index cd8a1b1..076f506 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -383,6 +383,13 @@ 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)))
+		return ERR_PTR(-EINVAL);
+
 	if (is_vm_hugetlb_page(vma))
 		return ERR_PTR(-EINVAL);
 
-- 
2.7.5

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^ permalink raw reply related	[flat|nested] 13+ messages in thread

end of thread, other threads:[~2017-07-24  8:50 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
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

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