On Thu, May 5, 2022 at 2:41 PM Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:
>
> There is a possibility for mdp5_get_global_state to return
> -EDEADLK when acquiring the modeset lock, but currently global_state in
> mdp5_mixer_release doesn't check for if an error is returned.
>
> To avoid a NULL dereference error, let's have mdp5_mixer_release
> check if an error is returned and propagate that error.
>
> Reported-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
Fixes: 7907a0d77cb4 ("drm/msm/mdp5: Use the new private_obj state")
Reviewed-by: Rob Clark <robdclark@xxxxxxxxx>
> ---
> drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c | 10 ++++++++--
> drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c | 15 +++++++++++----
> drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h | 4 ++--
> 3 files changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> index b966cd69f99d..fe2922c8d21b 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> @@ -612,9 +612,15 @@ static int mdp5_crtc_setup_pipeline(struct drm_crtc *crtc,
> if (ret)
> return ret;
>
> - mdp5_mixer_release(new_crtc_state->state, old_mixer);
> + ret = mdp5_mixer_release(new_crtc_state->state, old_mixer);
> + if (ret)
> + return ret;
> +
> if (old_r_mixer) {
> - mdp5_mixer_release(new_crtc_state->state, old_r_mixer);
> + ret = mdp5_mixer_release(new_crtc_state->state, old_r_mixer);
> + if (ret)
> + return ret;
> +
> if (!need_right_mixer)
> pipeline->r_mixer = NULL;
> }
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c
> index 954db683ae44..2536def2a000 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c
> @@ -116,21 +116,28 @@ int mdp5_mixer_assign(struct drm_atomic_state *s, struct drm_crtc *crtc,
> return 0;
> }
>
> -void mdp5_mixer_release(struct drm_atomic_state *s, struct mdp5_hw_mixer *mixer)
> +int mdp5_mixer_release(struct drm_atomic_state *s, struct mdp5_hw_mixer *mixer)
> {
> struct mdp5_global_state *global_state = mdp5_get_global_state(s);
> - struct mdp5_hw_mixer_state *new_state = &global_state->hwmixer;
> + struct mdp5_hw_mixer_state *new_state;
>
> if (!mixer)
> - return;
> + return 0;
> +
> + if (IS_ERR(global_state))
> + return PTR_ERR(global_state);
> +
> + new_state = &global_state->hwmixer;
>
> if (WARN_ON(!new_state->hwmixer_to_crtc[mixer->idx]))
> - return;
> + return -EINVAL;
>
> DBG("%s: release from crtc %s", mixer->name,
> new_state->hwmixer_to_crtc[mixer->idx]->name);
>
> new_state->hwmixer_to_crtc[mixer->idx] = NULL;
> +
> + return 0;
> }
>
> void mdp5_mixer_destroy(struct mdp5_hw_mixer *mixer)
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h b/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h
> index 43c9ba43ce18..545ee223b9d7 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h
> @@ -30,7 +30,7 @@ void mdp5_mixer_destroy(struct mdp5_hw_mixer *lm);
> int mdp5_mixer_assign(struct drm_atomic_state *s, struct drm_crtc *crtc,
> uint32_t caps, struct mdp5_hw_mixer **mixer,
> struct mdp5_hw_mixer **r_mixer);
> -void mdp5_mixer_release(struct drm_atomic_state *s,
> - struct mdp5_hw_mixer *mixer);
> +int mdp5_mixer_release(struct drm_atomic_state *s,
> + struct mdp5_hw_mixer *mixer);
>
> #endif /* __MDP5_LM_H__ */
> --
> 2.35.1
>
