linux-kernel - [PATCH 3.2 89/95] x86/mm/init.c: Fix devmem_is

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Date:   Sun, 16 Jul 2017 14:56:38 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "H. Peter Anvin" <hpa@...or.com>,
        yinghai@...nel.org, "T Makphaibulchoke" <tmac@...com>,
        dhowells@...hat.com, tiwai@...e.de,
        "Ingo Molnar" <mingo@...nel.org>
Subject: [PATCH 3.2 89/95] x86/mm/init.c: Fix devmem_is_allowed() off by one

3.2.91-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: T Makphaibulchoke <tmac@...com>

commit 73e8f3d7e2cb23614d5115703d76d8e54764b641 upstream.

Fixing an off-by-one error in devmem_is_allowed(), which allows
accesses to physical addresses 0x100000-0x100fff, an extra page
past 1MB.

Signed-off-by: T Makphaibulchoke <tmac@...com>
Acked-by: H. Peter Anvin <hpa@...or.com>
Cc: yinghai@...nel.org
Cc: tiwai@...e.de
Cc: dhowells@...hat.com
Link: http://lkml.kernel.org/r/1346210503-14276-1-git-send-email-tmac@hp.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/mm/init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -326,7 +326,7 @@ unsigned long __init_refok init_memory_m
  */
 int devmem_is_allowed(unsigned long pagenr)
 {
-	if (pagenr <= 256)
+	if (pagenr < 256)
 		return 1;
 	if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
 		return 0;