Re: [PATCH 1/1] mmc: Check to disable IOCTL when card is mounted

[Adrian Hunter <adrian.hunter@intel.com>]

On 28/12/11 12:46, Shashidhar hiremath wrote:
> From: Shashidhar Hiremath <shashidharh@vayavyalabs.com>
> 
> The Patch adds a check to disable the IOCTL from running when the card is mounted
> or device is opened elsewhere.

What if someone wants to do that.

Generally the kernel does not prevent access to raw block devices
just because a file system is mounted on them, so I guess MMC should
not either.


> 
> Signed-off-by: Shashidhar Hiremath <shashidharh@vayavyalabs.com>
> ---
>  drivers/mmc/card/block.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 0cad48a..e680929 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -387,6 +387,12 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>  		err = -EINVAL;
>  		goto cmd_done;
>  	}
> +	/* Disallow the IOCTL run if card is already mounted or device is
> +	 * opened elsewhere */
> +	if (md->usage > 3) {
> +		err = -EINVAL;
> +		goto cmd_done;
> +	}

Checking the usage will not work consistently e.g.
if there is a sysfs access or another ioctl access at the
same time, or just some other kernel user of the device.

>  
>  	card = md->queue.card;
>  	if (IS_ERR(card)) {