[PATCH] Fix an overflow in range_to_mtrr func

From: Zhenzhong Duan
Date: Mon May 28 2012 - 08:29:19 EST


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@xxxxxxxxxx>
---
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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