Re: [PATCH v3 1/2] drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On 06/05/2022 01:01, Rob Clark wrote:
> On Thu, May 5, 2022 at 2:41 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
> >
> > Changes since v2:
> > - Return 0 in case where hwpipe is NULL as this is considered normal
> >    behavior
> > - Added 2nd patch in series to fix a similar NULL dereference issue in
> >    mdp5_mixer_release
> >
> > 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>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > ---
> >   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..a4f5cb90f3e8 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 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


--
With best wishes
Dmitry