linux-kernel - [PATCH 2/2][RFC] mmc: cast unsigned int to typeof(sector

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Message-ID: <87sicb5b33.wl%kuninori.morimoto.gx@renesas.com>
Date:	Wed, 8 Apr 2015 07:33:40 +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 2/2][RFC] mmc: cast unsigned int to typeof(sector_t) to avoid unexpected error

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

card->csd.capacity is defined as "unsigned int",
and, sector_t is defined as "u64" or "unsigned long" (depends on CONFIG_LBDAF)
sector_t data might have strange data if first bit of unsigned int
was 1. this patch cast it to typeof(sector_t)

ex) if sector_t was u64

        unsigned int data;
        sector_t sector;

        data = 0x80000000;
        sector = (data << 8); // 0xffffff8000000000
        sector = (((typeof(sector_t))data) << 8); // 0x8000000000

Reported-by: coverity <http://www.coverity.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
---
 drivers/mmc/card/block.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index c69afb5..4d09b0c 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -2205,7 +2205,7 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
 		 * The CSD capacity field is in units of read_blkbits.
 		 * set_capacity takes units of 512 bytes.
 		 */
-		size = card->csd.capacity << (card->csd.read_blkbits - 9);
+		size = (typeof(sector_t))card->csd.capacity << (card->csd.read_blkbits - 9);
 	}
 
 	return mmc_blk_alloc_req(card, &card->dev, size, false, NULL,
-- 
1.9.1

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