linux-kernel - Re: [PATCH] drm/display/dp_mst: Fix missing check for return value of drm_atomic_get_mst_payload

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <b441d8e53c9b5e95da447b3681bb9143448388fc.camel@redhat.com>
Date:   Tue, 20 Jun 2023 15:48:25 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Chenyuan Mi <cymi20@...an.edu.cn>, airlied@...il.com
Cc:     daniel@...ll.ch, jani.nikula@...el.com, Wayne.Lin@....com,
        imre.deak@...el.com, alexander.deucher@....com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/display/dp_mst: Fix missing check for return value
 of drm_atomic_get_mst_payload_state()

Hm, I suppose it's not -impossible- for this to return NULL, but if it does
return NULL that absolutely means something broke well before this point in
the code. More comments below:

On Wed, 2023-06-14 at 09:09 -0700, Chenyuan Mi wrote:
> The drm_atomic_get_mst_payload_state() function may
> return NULL, which may cause null pointer deference,
> and most other callsites of drm_atomic_get_mst_payload_state()
> do Null check. Add Null check for return value of
> drm_atomic_get_mst_payload_state().
> 
> Found by our static analysis tool.
> 
> Signed-off-by: Chenyuan Mi <cymi20@...an.edu.cn>
> ---
>  drivers/gpu/drm/display/drm_dp_mst_topology.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index 38dab76ae69e..27f4bcf409ea 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -4434,6 +4434,8 @@ void drm_dp_mst_atomic_wait_for_dependencies(struct drm_atomic_state *state)
>  
>  			new_payload = drm_atomic_get_mst_payload_state(new_mst_state,
>  								       old_payload->port);
> +			if (!new_payload)
> +				continue;

Could you change this check to:

	if (drm_WARN_ON(state->dev, !new_payload))

>  			new_payload->vc_start_slot = old_payload->vc_start_slot;
>  		}
>  	}

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat