Re: [PATCH v6 1/3] Staging: zram: Fix access of NULL pointer

From: Weijie Yang
Date: Mon Oct 28 2013 - 09:45:47 EST


On Mon, Oct 28, 2013 at 8:21 PM, Rashika Kheria
<rashika.kheria@xxxxxxxxx> wrote:
> This patch fixes the bug in reset_store caused by accessing NULL pointer.
> Hence, It introduces a check for bdev. It also removes unnecessary check
> of bdev for fsync_bdev().
>
> Signed-off-by: Rashika Kheria <rashika.kheria@xxxxxxxxx>
> ---
>
> This revision fixes the following issues of the previous revision-
> Seperating patches into Bug fix and Smatch fix
>
> 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..d640a8f 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 -EBUSY;
> +

I am not sure how does it happen. Would you please make it clear to me?

Thanks

> /* 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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