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SubjectRe: [PATCH v7 1/3] Staging: zram: Fix access of NULL pointer
On 10/30/2013 12:10 AM, Rashika Kheria wrote:
> 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@vger.kernel.org
> Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>

> ---
>
> This patch fixes the following issues of the previous revision-
> Better Description
>
> 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;
> +
> /* 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;
>



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