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[PATCH v2 5/5] mremap: simplify the "overlap" check in mremap_to()

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Minor, but this check is overcomplicated. Two half-intervals do NOT
overlap if END1 <= START2 || END2 <= START1, mremap_to() just needs
to negate this check.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
---
 mm/mremap.c |    9 ++-------
 1 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index d3f42be..5a71cce 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -407,13 +407,8 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 	if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 		goto out;
 
-	/* Check if the location we're moving into overlaps the
-	 * old location at all, and fail if it does.
-	 */
-	if ((new_addr <= addr) && (new_addr+new_len) > addr)
-		goto out;
-
-	if ((addr <= new_addr) && (addr+old_len) > new_addr)
+	/* Ensure the old/new locations do not overlap */
+	if (addr + old_len > new_addr && new_addr + new_len > addr)
 		goto out;
 
 	ret = do_munmap(mm, new_addr, new_len);
-- 
1.5.5.1

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[PATCH v2 0/5] mremap fix/cleanups Oleg Nesterov <oleg@redhat.com> - 2015-07-02 01:10 +0200
  [PATCH v2 4/5] mremap: don't do uneccesary checks if new_len ==  old_len Oleg Nesterov <oleg@redhat.com> - 2015-07-02 01:10 +0200
  [PATCH v2 2/5] mm: move ->mremap() from file_operations to  vm_operations_struct Oleg Nesterov <oleg@redhat.com> - 2015-07-02 01:10 +0200
  [PATCH v2 1/5] mremap: don't leak new_vma if f_op->mremap() fails Oleg Nesterov <oleg@redhat.com> - 2015-07-02 01:10 +0200
  [PATCH v2 3/5] mremap: don't do mm_populate(new_addr) on failure Oleg Nesterov <oleg@redhat.com> - 2015-07-02 01:10 +0200
  [PATCH v2 5/5] mremap: simplify the "overlap" check in mremap_to() Oleg Nesterov <oleg@redhat.com> - 2015-07-02 01:10 +0200

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