Hello,
On Mon, Oct 21, 2013 at 02:52:41PM +0530, Rashika Kheria wrote:
> This patch fixes the following Smatch warning in zram_drv.c-
> drivers/staging/zram/zram_drv.c:663
> reset_store() warn: variable dereferenced before check 'bdev' (see line 652)
> drivers/staging/zram/zram_drv.c:899
> destroy_device() warn: variable dereferenced before check 'zram->disk' (see line 896)
>
> Signed-off-by: Rashika Kheria <rashika.kheria@xxxxxxxxx>
> ---
>
> This revision fixes the following issues of the previous revision-
> Not included null check
>
> drivers/staging/zram/zram_drv.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index 2c4ed52..5594d5b 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'm not an expert on sysfs and block so it's hard to understand
when we could see NULL bdev in reset handler.
I hope others could answer it.
Another thing, when I review the code, I found it has a bug.
reset_store doesn't put refcount by getting one by bdget_disk.
It should be fixed, I think.
> /* 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;
> @@ -893,10 +895,9 @@ out:
>
> static void destroy_device(struct zram *zram)
> {
> - sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
> - &zram_disk_attr_group);
> -
> if (zram->disk) {
> + sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
> + &zram_disk_attr_group);
Is it really necessary to check zram->disk and zram->queue in this function?
As I see code roughly, it seems to be not necessary but need double check.
If so, please remove the check code.
> del_gendisk(zram->disk);
> put_disk(zram->disk);
> }
> --
> 1.7.9.5
>
--
Kind regards,
Minchan Kim
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