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

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Date:	Mon, 28 Oct 2013 21:45:42 +0800
From:	Weijie Yang <weijie.yang.kh@...il.com>
To:	Rashika Kheria <rashika.kheria@...il.com>
Cc:	opw-kernel@...glegroups.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Minchan Kim <minchan@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchand@...hat.com>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 1/3] Staging: zram: Fix access of NULL pointer

On Mon, Oct 28, 2013 at 8:21 PM, Rashika Kheria
<rashika.kheria@...il.com> 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@...il.com>
> ---
>
> 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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