[PATCH v2 2/4] drm: NULL pointer dereference [null-pointer-deref] (CWE 476) problem

[Daniel Vetter]

On Mon, Feb 12, 2018 at 02:51:42PM -0500, Joe Moriarty wrote:
> The Parfait (version 2.1.0) static code analysis tool found the
> following NULL pointer derefernce problem.
> 
> - drivers/gpu/drm/drm_dp_mst_topology.c
> The call to drm_dp_calculate_rad() in function drm_dp_port_setup_pdt()
> could result in a NULL pointer being returned to port->mstb due to a
> failure to allocate memory for port->mstb.
> 
> Signed-off-by: Joe Moriarty <joe.moriarty at oracle.com>
> Reviewed-by: Steven Sistare <steven.sistare at oracle.com>

Small allocations don't fail, so just pushed to drm-misc-next, not -fixes.

Thanks, Daniel

> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 70dcfa58d3c2..ec503d416062 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1082,10 +1082,12 @@ static bool drm_dp_port_setup_pdt(struct drm_dp_mst_port *port)
>  		lct = drm_dp_calculate_rad(port, rad);
>  
>  		port->mstb = drm_dp_add_mst_branch_device(lct, rad);
> -		port->mstb->mgr = port->mgr;
> -		port->mstb->port_parent = port;
> +		if (port->mstb) {
> +			port->mstb->mgr = port->mgr;
> +			port->mstb->port_parent = port;
>  
> -		send_link = true;
> +			send_link = true;
> +		}
>  		break;
>  	}
>  	return send_link;
> -- 
> 2.15.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch