linux-kernel - [PATCH v9 1/2] Staging: zram: Fix access of NULL pointer

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Message-Id: <3d7e050910ca994862e7880b4bd3681267681b56.1383220461.git.rashika.kheria@gmail.com>
Date:	Thu, 31 Oct 2013 17:26:46 +0530
From:	Rashika Kheria <rashika.kheria@...il.com>
To:	opw-kernel@...glegroups.com, Minchan Kim <minchan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchand@...hat.com>,
	linux-kernel@...r.kernel.org
Cc:	stable@...r.kernel.org
Subject: [PATCH v9 1/2] Staging: zram: Fix access of NULL pointer

This patch fixes the bug in reset_store caused by accessing NULL pointer.

The bdev gets its value from bdget_disk() which could fail when memory
pressure is severe and hence can return NULL because allocation of
inode in bdget could fail.

Hence, this patch introduces a check for bdev to prevent reference to a
NULL pointer in the later part of the code. It also removes unnecessary
check of bdev for fsync_bdev().

Cc: stable@...r.kernel.org
Acked-by: Jerome Marchand <jmarchan@...hat.com> 
Signed-off-by: Rashika Kheria <rashika.kheria@...il.com>
---
 drivers/staging/zram/zram_drv.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 2c4ed52..012ba15 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -648,6 +648,9 @@ static ssize_t reset_store(struct device *dev,
 	zram = dev_to_zram(dev);
 	bdev = bdget_disk(zram->disk, 0);
 
+	if (!bdev)
+		return -ENOMEM;
+
 	/* Do not reset an active device! */
 	if (bdev->bd_holders)
 		return -EBUSY;
@@ -660,8 +663,7 @@ static ssize_t reset_store(struct device *dev,
 		return -EINVAL;
 
 	/* Make sure all pending I/O is finished */
-	if (bdev)
-		fsync_bdev(bdev);
+	fsync_bdev(bdev);
 
 	zram_reset_device(zram, true);
 	return len;
-- 
1.7.9.5

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