linux-kernel - [PATCH] mtd: blktrans: fix integer overflow

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Date:	Fri, 21 Aug 2015 22:57:31 +0800
From:	Peng Fan <van.freenix@...il.com>
To:	dwmw2@...radead.org, computersforpeace@...il.com
Cc:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	van.freenix@...il.com
Subject: [PATCH] mtd: blktrans: fix integer overflow

In drivers/mtd/mtd_blkdevs.c:
406	set_capacity(gd, (new->size * tr->blksize) >> 9);
The type of new->size is unsigned long and the type of tr->blksize is int,
the result of 'new->size * tr->blksize' may exceed ULONG_MAX on 32bit
machines.

I use nand chip MT29F32G08CBADBWP which is 4GB and the parameters passed
to kernel is 'mtdparts=gpmi-nand:-(user)', the whole nand chip will be
treated as a 4GB mtd partition. new->size is 0x800000 and tr->blksize is
0x200, 'new->size * tr->blksize' however is 0. This is what we do not want
to see.

Change the type of entry size of mtd_blktrans_dev to unsigned long long
to fix the overflow issue.

Signed-off-by: Peng Fan <van.freenix@...il.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Brian Norris <computersforpeace@...il.com>
---
 include/linux/mtd/blktrans.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mtd/blktrans.h b/include/linux/mtd/blktrans.h
index e93837f..3853d74 100644
--- a/include/linux/mtd/blktrans.h
+++ b/include/linux/mtd/blktrans.h
@@ -38,7 +38,7 @@ struct mtd_blktrans_dev {
 	struct mutex lock;
 	int devnum;
 	bool bg_stop;
-	unsigned long size;
+	unsigned long long size;
 	int readonly;
 	int open;
 	struct kref ref;
-- 
1.8.4

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