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")
Link: http://lkml.kernel.org/r/1492042622-12074-1-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index dceb5ed..03a7408 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -928,7 +928,7 @@ 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;