Re: [PATCH 1/5] cxl/hdm: Fail upon detecting 0-sized decoders

[Dave Jiang <dave.jiang@intel.com>]

On 4/14/23 11:53 AM, Dan Williams wrote:
> Decoders committed with 0-size lead to later crashes on shutdown as
> __cxl_dpa_release() assumes a 'struct resource' has been established in
> the in 'cxlds->dpa_res'. Just fail the driver load in this instance
> since there are deeper problems with the enumeration or the setup when
> this happens.
> 
> Fixes: 9c57cde0dcbd ("cxl/hdm: Enumerate allocated DPA")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>   drivers/cxl/core/hdm.c |   15 ++++++++++++---
>   1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 02cc2c38b44b..35b338b716fe 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -269,8 +269,11 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>   
>   	lockdep_assert_held_write(&cxl_dpa_rwsem);
>   
> -	if (!len)
> -		goto success;
> +	if (!len) {
> +		dev_warn(dev, "decoder%d.%d: empty reservation attempted\n",
> +			 port->id, cxled->cxld.id);
> +		return -EINVAL;
> +	}
>   
>   	if (cxled->dpa_res) {
>   		dev_dbg(dev, "decoder%d.%d: existing allocation %pr assigned\n",
> @@ -323,7 +326,6 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>   		cxled->mode = CXL_DECODER_MIXED;
>   	}
>   
> -success:
>   	port->hdm_end++;
>   	get_device(&cxled->cxld.dev);
>   	return 0;
> @@ -833,6 +835,13 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>   				 port->id, cxld->id);
>   			return -ENXIO;
>   		}
> +
> +		if (size == 0) {
> +			dev_warn(&port->dev,
> +				 "decoder%d.%d: Committed with zero size\n",
> +				 port->id, cxld->id);
> +			return -ENXIO;
> +		}
>   		port->commit_end = cxld->id;
>   	} else {
>   		/* unless / until type-2 drivers arrive, assume type-3 */
>