linux-kernel - [PATCH 1/3] zram: fix operator precedence to get offset

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Date:   Thu, 13 Apr 2017 09:17:00 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        <kernel-team@....com>, Minchan Kim <minchan@...nel.org>,
        <stable@...r.kernel.org>
Subject: [PATCH 1/3] zram: fix operator precedence to get offset

In zram_rw_page, the logic to get offset is wrong by operator precedence
(i.e., "<<" is higher than "&"). With wrong offset, zram can corrupt the
user's data. This patch fixes it.

Fixes: 8c7f01025 ("zram: implement rw_page operation of zram")
Cc: stable@...r.kernel.org
Signed-off-by: Minchan Kim <minchan@...nel.org>
---
 drivers/block/zram/zram_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 9e2199060040..83c38a123242 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -930,7 +930,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
 	}
 
 	index = sector >> SECTORS_PER_PAGE_SHIFT;
-	offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
+	offset = (sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 
 	bv.bv_page = page;
 	bv.bv_len = PAGE_SIZE;
-- 
2.7.4