Re: [PATCH] scsi_dh: only attach to SCSI devices

[Bart Van Assche <Bart.VanAssche@sandisk.com>]

On Thu, 2017-02-16 at 08:33 +0100, Hannes Reinecke wrote:
> Any device might be setting a queuedata structure, so we need to
> check if the queuedata really belongs to a SCSI device before
> proceeding.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.com>
> ---
>  drivers/scsi/scsi_dh.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_dh.c b/drivers/scsi/scsi_dh.c
> index b8d3b97..da104ed 100644
> --- a/drivers/scsi/scsi_dh.c
> +++ b/drivers/scsi/scsi_dh.c
> @@ -226,7 +226,9 @@ static struct scsi_device *get_sdev_from_queue(struct request_queue *q)
>  
>  	spin_lock_irqsave(q->queue_lock, flags);
>  	sdev = q->queuedata;
> -	if (!sdev || !get_device(&sdev->sdev_gendev))
> +	if (!sdev ||
> +	    !scsi_is_sdev_device(&sdev->sdev_gendev) ||
> +	    !get_device(&sdev->sdev_gendev))
>  		sdev = NULL;
>  	spin_unlock_irqrestore(q->queue_lock, flags);

Hello Hannes,

Sorry but this approach looks wrong to me. A block driver can store any data
in .queuedata, even data that would cause the scsi_is_sdev_device() function
to crash.

Bart.