Re: [PATCH] drm/mst: Fix NULL pointer dereference at drm_dp_add_payload_part2

[Harry Wentland <harry.wentland@amd.com>]

On 2024-03-07 01:29, Wayne Lin wrote:
> [Why]
> Commit:
> - commit 5aa1dfcdf0a4 ("drm/mst: Refactor the flow for payload allocation/removement")
> accidently overwrite the commit
> - commit 54d217406afe ("drm: use mgr->dev in drm_dbg_kms in drm_dp_add_payload_part2")
> which cause regression.
> 
> [How]
> Recover the original NULL fix and remove the unnecessary input parameter 'state' for
> drm_dp_add_payload_part2().
> 
> Fixes: 5aa1dfcdf0a4 ("drm/mst: Refactor the flow for payload allocation/removement")
> Reported-by: Leon Weiß <leon.weiss@ruhr-uni-bochum.de>
> Link: https://lore.kernel.org/r/38c253ea42072cc825dc969ac4e6b9b600371cc8.camel@ruhr-uni-bochum.de/
> Cc: lyude@redhat.com
> Cc: imre.deak@intel.com
> Cc: stable@vger.kernel.org
> Cc: regressions@lists.linux.dev
> Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>

I haven't been deep in MST code in a while but this all looks
pretty straightforward and good.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 2 +-
>  drivers/gpu/drm/display/drm_dp_mst_topology.c             | 4 +---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c               | 2 +-
>  drivers/gpu/drm/nouveau/dispnv50/disp.c                   | 2 +-
>  include/drm/display/drm_dp_mst_helper.h                   | 1 -
>  5 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> index c27063305a13..2c36f3d00ca2 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> @@ -363,7 +363,7 @@ void dm_helpers_dp_mst_send_payload_allocation(
>  	mst_state = to_drm_dp_mst_topology_state(mst_mgr->base.state);
>  	new_payload = drm_atomic_get_mst_payload_state(mst_state, aconnector->mst_output_port);
>  
> -	ret = drm_dp_add_payload_part2(mst_mgr, mst_state->base.state, new_payload);
> +	ret = drm_dp_add_payload_part2(mst_mgr, new_payload);
>  
>  	if (ret) {
>  		amdgpu_dm_set_mst_status(&aconnector->mst_status,
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index 03d528209426..95fd18f24e94 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -3421,7 +3421,6 @@ EXPORT_SYMBOL(drm_dp_remove_payload_part2);
>  /**
>   * drm_dp_add_payload_part2() - Execute payload update part 2
>   * @mgr: Manager to use.
> - * @state: The global atomic state
>   * @payload: The payload to update
>   *
>   * If @payload was successfully assigned a starting time slot by drm_dp_add_payload_part1(), this
> @@ -3430,14 +3429,13 @@ EXPORT_SYMBOL(drm_dp_remove_payload_part2);
>   * Returns: 0 on success, negative error code on failure.
>   */
>  int drm_dp_add_payload_part2(struct drm_dp_mst_topology_mgr *mgr,
> -			     struct drm_atomic_state *state,
>  			     struct drm_dp_mst_atomic_payload *payload)
>  {
>  	int ret = 0;
>  
>  	/* Skip failed payloads */
>  	if (payload->payload_allocation_status != DRM_DP_MST_PAYLOAD_ALLOCATION_DFP) {
> -		drm_dbg_kms(state->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
> +		drm_dbg_kms(mgr->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
>  			    payload->port->connector->name);
>  		return -EIO;
>  	}
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 53aec023ce92..2fba66aec038 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -1160,7 +1160,7 @@ static void intel_mst_enable_dp(struct intel_atomic_state *state,
>  	if (first_mst_stream)
>  		intel_ddi_wait_for_fec_status(encoder, pipe_config, true);
>  
> -	drm_dp_add_payload_part2(&intel_dp->mst_mgr, &state->base,
> +	drm_dp_add_payload_part2(&intel_dp->mst_mgr,
>  				 drm_atomic_get_mst_payload_state(mst_state, connector->port));
>  
>  	if (DISPLAY_VER(dev_priv) >= 12)
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index 0c3d88ad0b0e..88728a0b2c25 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -915,7 +915,7 @@ nv50_msto_cleanup(struct drm_atomic_state *state,
>  		msto->disabled = false;
>  		drm_dp_remove_payload_part2(mgr, new_mst_state, old_payload, new_payload);
>  	} else if (msto->enabled) {
> -		drm_dp_add_payload_part2(mgr, state, new_payload);
> +		drm_dp_add_payload_part2(mgr, new_payload);
>  		msto->enabled = false;
>  	}
>  }
> diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
> index 9b19d8bd520a..6c9145abc7e2 100644
> --- a/include/drm/display/drm_dp_mst_helper.h
> +++ b/include/drm/display/drm_dp_mst_helper.h
> @@ -851,7 +851,6 @@ int drm_dp_add_payload_part1(struct drm_dp_mst_topology_mgr *mgr,
>  			     struct drm_dp_mst_topology_state *mst_state,
>  			     struct drm_dp_mst_atomic_payload *payload);
>  int drm_dp_add_payload_part2(struct drm_dp_mst_topology_mgr *mgr,
> -			     struct drm_atomic_state *state,
>  			     struct drm_dp_mst_atomic_payload *payload);
>  void drm_dp_remove_payload_part1(struct drm_dp_mst_topology_mgr *mgr,
>  				 struct drm_dp_mst_topology_state *mst_state,