mremap: simplify the "overlap" check in mremap_to()

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 <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Benjamin LaHaise <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jeff Moyer <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Laurent Dufour <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 2 insertions, 7 deletions

diff --git a/mm/mremap.c b/mm/mremap.c
index d3f42bece564..5a71cce8c6ea 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);