linux-kernel - [PATCH v2] Fix an overflow in range_to

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Date:	Wed, 30 May 2012 12:52:15 +0800
From:	"zhenzhong.duan" <zhenzhong.duan@...cle.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	zhenzhong.duan@...cle.com, mingo@...hat.com, x86@...nel.org,
	tglx@...utronix.de, hpa@...or.com, Feng Jin <joe.jin@...cle.com>,
	ethan.zhao@...cle.com, linux-kernel@...r.kernel.org
Subject: [PATCH v2] Fix an overflow in range_to_mtrr func

When boot on sun G5+ with 4T mem, see an overflow in mtrr cleanup as below.

*BAD*gran_size: 2G      chunk_size: 2G  num_reg: 10     lose cover RAM:
-18014398505283592M

This is because 1<<31 sign extended. Use 64bit constant to fix it.
Useful for mem larger than or equal to 4T.

-v2: Use 64bit constant instead of explicit type conversion as suggested
by Yinghai. Description updated too.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
---
  arch/x86/kernel/cpu/mtrr/cleanup.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c
b/arch/x86/kernel/cpu/mtrr/cleanup.c
index ac140c7..853a4c6 100644
--- a/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -266,7 +266,7 @@ range_to_mtrr(unsigned int reg, unsigned long
range_startk,
  		if (align > max_align)
  			align = max_align;

-		sizek = 1 << align;
+		sizek = 1UL << align;
  		if (debug_print) {
  			char start_factor = 'K', size_factor = 'K';
  			unsigned long start_base, size_base;
-- 1.7.3
--
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