linux-kernel - [PATCH 4/4] mremap: simplify the "overlap" check in mremap

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Message-ID: <20150619231921.GA25894@redhat.com>
Date:	Sat, 20 Jun 2015 01:19:21 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Hugh Dickins <hughd@...gle.com>,
	Jeff Moyer <jmoyer@...hat.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] 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 <oleg@...hat.com>
---
 mm/mremap.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index 2416721..ed1b13a 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -406,10 +406,7 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 	/* 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)
+	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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