linux-kernel - [PATCH 1/2][RFC] mmc: cast u8 to unsigned long long to avoid unexpected error

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Date:	Wed, 8 Apr 2015 07:33:21 +0000
From:	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
CC:	<ryusuke.sakato.bx@...esas.com>,
	<yoshihiro.shimoda.uh@...esas.com>,
	<hiroyuki.yokoyama.vx@...esas.com>,
	<takeshi.kihara.df@...esas.com>,
	"Jaehoon Chung" <jh80.chung@...sung.com>,
	Chris Ball <chris@...ntf.net>,
	"Seungwon Jeon" <tgih.jun@...sung.com>,
	"Grégory Soutadé" <gsoutade@...tion.com>,
	<linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>
Subject: [PATCH 1/2][RFC] mmc: cast u8 to unsigned long long to avoid unexpected error

From: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>

card->ext_csd.enhanced_area_offset is defined as "unsigned long long",
and, ext_csd[] is defined as u8.
unsigned long long data might have strange data if first bit of ext_csd[]
was 1. this patch cast it to (unsigned long long)
ex)
        u8  data8;
        u64 data64;

        data8 = 0x80;
        data64 = (data8 << 24); // 0xffffffff80000000
        data64 = (((unsigned long long)data8) << 24); // 0x80000000;

Reported-by: coverity <http://www.coverity.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
---
 drivers/mmc/core/mmc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 1d41e85..3c663a2 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -265,8 +265,10 @@ static void mmc_manage_enhanced_area(struct mmc_card *card, u8 *ext_csd)
 			 * calculate the enhanced data area offset, in bytes
 			 */
 			card->ext_csd.enhanced_area_offset =
-				(ext_csd[139] << 24) + (ext_csd[138] << 16) +
-				(ext_csd[137] << 8) + ext_csd[136];
+				(((unsigned long long)ext_csd[139]) << 24) +
+				(((unsigned long long)ext_csd[138]) << 16) +
+				(((unsigned long long)ext_csd[137]) << 8) +
+				(((unsigned long long)ext_csd[136]));
 			if (mmc_card_blockaddr(card))
 				card->ext_csd.enhanced_area_offset <<= 9;
 			/*
-- 
1.9.1

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