On Wed, May 4, 2022 at 6:55 PM Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:
>
> mdp5_get_global_state runs the risk of hitting a -EDEADLK when acquiring
> the modeset lock, but currently mdp5_pipe_release doesn't check for if
> an error is returned. Because of this, there is a possibility of
> mdp5_pipe_release hitting a NULL dereference error.
>
> To avoid this, let's have mdp5_pipe_release check if
> mdp5_get_global_state returns an error and propogate that error.
>
> Changes since v1:
> - Separated declaration and initialization of *new_state to avoid
> compiler warning
> - Fixed some spelling mistakes in commit message
>
Note that mdp5_mixer_release() needs the same treatment.. one more comment below
> Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c | 15 +++++++++++----
> drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h | 2 +-
> drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c | 20 ++++++++++++++++----
> 3 files changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> index ba6695963aa6..97887a2be082 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> @@ -119,18 +119,23 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
> return 0;
> }
>
> -void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
> +int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
> {
> struct msm_drm_private *priv = s->dev->dev_private;
> struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
> struct mdp5_global_state *state = mdp5_get_global_state(s);
> - struct mdp5_hw_pipe_state *new_state = &state->hwpipe;
> + struct mdp5_hw_pipe_state *new_state;
>
> if (!hwpipe)
> - return;
> + return -EINVAL;
At least per the current code, !hwpipe is "normal".. I think that fits
the model of things like kfree(NULL), so lets make this just return 0
> +
> + if (IS_ERR(state))
> + return PTR_ERR(state);
> +
> + new_state = &state->hwpipe;
>
> if (WARN_ON(!new_state->hwpipe_to_plane[hwpipe->idx]))
> - return;
> + return -EINVAL;
>
> DBG("%s: release from plane %s", hwpipe->name,
> new_state->hwpipe_to_plane[hwpipe->idx]->name);
> @@ -141,6 +146,8 @@ void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
> }
>
> new_state->hwpipe_to_plane[hwpipe->idx] = NULL;
> +
> + return 0;
> }
>
> void mdp5_pipe_destroy(struct mdp5_hw_pipe *hwpipe)
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> index 9b26d0761bd4..cca67938cab2 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> @@ -37,7 +37,7 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
> uint32_t caps, uint32_t blkcfg,
> struct mdp5_hw_pipe **hwpipe,
> struct mdp5_hw_pipe **r_hwpipe);
> -void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
> +int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
>
> struct mdp5_hw_pipe *mdp5_pipe_init(enum mdp5_pipe pipe,
> uint32_t reg_offset, uint32_t caps);
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> index 228b22830970..979458482841 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> @@ -311,12 +311,24 @@ static int mdp5_plane_atomic_check_with_state(struct drm_crtc_state *crtc_state,
> mdp5_state->r_hwpipe = NULL;
>
>
> - mdp5_pipe_release(state->state, old_hwpipe);
> - mdp5_pipe_release(state->state, old_right_hwpipe);
> + ret = mdp5_pipe_release(state->state, old_hwpipe);
> + if (ret)
> + return ret;
> +
> + ret = mdp5_pipe_release(state->state, old_right_hwpipe);
> + if (ret)
> + return ret;
> +
> }
> } else {
> - mdp5_pipe_release(state->state, mdp5_state->hwpipe);
> - mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
> + ret = mdp5_pipe_release(state->state, mdp5_state->hwpipe);
> + if (ret)
> + return ret;
> +
> + ret = mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
> + if (ret)
> + return ret;
> +
> mdp5_state->hwpipe = mdp5_state->r_hwpipe = NULL;
> }
>
> --
> 2.35.1
>
