Re: [PATCH v4 2/2] cxl/port: Fix uninitialized coordinates reported for RCDs

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 31 Aug 2026 17:22:16 +0800
Guixin Liu <kanie@linux.alibaba.com> wrote:

> cxl_endpoint_get_perf_coordinates() returns success for a Restricted CXL
> Device without calculating coordinates, so the caller's output array is
> left uninitialized. Callers treat it as valid and can expose the stack
> residue as access coordinates.
> 
> Initialize the coordinates to zero before returning for an RCD. Zeroing in
> the helper rather than at the caller keeps the @coord output contract the
> exported function documents.
> 
> Reported by the Sashiko review bot.
> 
> Fixes: 5d211c709059 ("cxl: Fix cxl_endpoint_get_perf_coordinate() support for RCH")
> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
> Reviewed-by: Richard Cheng <icheng@nvidia.com>
Makes sense.  You 'could' add an __at_least marking to the coord parameter of this
function just to make it clear this is the size (well technically the min size, but
that's fine).  Not important though and not really part of this fix.

Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

> ---
>  drivers/cxl/core/port.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 625e4aa427db..fea43a92744c 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -2394,8 +2394,10 @@ int cxl_endpoint_get_perf_coordinates(struct cxl_port *port,
>  	 * Skip calculation for RCD. Expectation is HMAT already covers RCD case
>  	 * since RCH does not support hotplug.
>  	 */
> -	if (cxlmd->cxlds->rcd)
> +	if (cxlmd->cxlds->rcd) {
> +		memset(coord, 0, sizeof(*coord) * ACCESS_COORDINATE_MAX);
>  		return 0;
> +	}
>  
>  	/*
>  	 * Exit the loop when the parent port of the current iter port is cxl