Re: [PATCH v2] dm: don't allow ioctls to targets that don't map to whole devices

[Mike Snitzer <snitzer@redhat.com>]

On Fri, Feb 03 2017 at 11:22am -0500,
Christoph Hellwig <hch@lst.de> wrote:

> .. at least for unprivileged users.  Before we called into the SCSI
> ioctl code to allow excemptions for a few SCSI passthrough ioctls,
> but this is pretty unsafe and except for this call dm knows nothing
> about SCSI ioctls.
> 
> As the SCSI ioctl code is now optional, we really don't want to
> drag it in for DM, and the exception is not very useful anyway.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Mike Snitzer <snitzer@redhat.com>
> ---
>  drivers/md/dm.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 9e958bc94fed..fd4331aa2e19 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -465,13 +465,16 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
>  
>  	if (r > 0) {
>  		/*
> -		 * Target determined this ioctl is being issued against
> -		 * a logical partition of the parent bdev; so extra
> -		 * validation is needed.
> +		 * Target determined this ioctl is being issued against a
> +		 * subset of the parent bdev; require extra privileges.
>  		 */
> -		r = scsi_verify_blk_ioctl(NULL, cmd);
> -		if (r)
> +		if (!capable(CAP_SYS_RAWIO)) {
> +			DMWARN_LIMIT(
> +	"%s: sending ioctl %x to DM device without required privilege.\n",
> +				current->comm, cmd);
> +			r = -ENOIOCTLCMD;
>  			goto out;
> +		}
>  	}
>  
>  	r =  __blkdev_driver_ioctl(bdev, mode, cmd, arg);
> -- 
> 2.11.0
> 

Sorry, should've been clearer (or just sent an incremental patch) but
DMWARN et al don't require a newline at the end of their message strings.