[PATCH 3.2 094/185] Staging: zram: Fix access of NULL pointer

[Ben Hutchings]

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Rashika Kheria <rashika.kheria@xxxxxxxxx>

commit 46a51c80216cb891f271ad021f59009f34677499 upstream.

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().

Acked-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
Signed-off-by: Rashika Kheria <rashika.kheria@xxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/staging/zram/zram_sysfs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/staging/zram/zram_sysfs.c
+++ b/drivers/staging/zram/zram_sysfs.c
@@ -95,6 +95,9 @@ static ssize_t reset_store(struct device
 	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;
@@ -107,8 +110,7 @@ static ssize_t reset_store(struct device
 		return -EINVAL;
 
 	/* Make sure all pending I/O is finished */
-	if (bdev)
-		fsync_bdev(bdev);
+	fsync_bdev(bdev);
 
 	down_write(&zram->init_lock);
 	if (zram->init_done)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/