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

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Date:	Mon, 28 May 2012 05:29:11 -0700 (PDT)
From:	Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:	<mingo@...hat.com>, <x86@...nel.org>, <yinghai@...nel.org>,
	<tglx@...utronix.de>, <hpa@...or.com>
Cc:	Feng Jin <joe.jin@...cle.com>, <ethan.zhao@...cle.com>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] Fix an overflow in range_to_mtrr func

When boot x86_64 kernel 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 explicit type conversion to force a 64bit constant to fix it.
Useful for mem larger than or equal to 4T.

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

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