Re: [PATCH v2 2/3] drm/ingenic: Register devm action to cleanup encoders

[Paul Cercueil]

Le mer. 20 janv. 2021 à 15:04, Daniel Vetter <daniel@xxxxxxxx> a 
écrit :
> On Wed, Jan 20, 2021 at 2:21 PM Paul Cercueil <paul@xxxxxxxxxxxxxxx> 
> wrote:
> >  Le mer. 20 janv. 2021 à 14:01, Daniel Vetter <daniel@xxxxxxxx> a
> >  écrit :
> >  > On Wed, Jan 20, 2021 at 1:36 PM Paul Cercueil 
> > <paul@xxxxxxxxxxxxxxx>
> >  > wrote:
> >  >>
> >  >>  Since the encoders have been devm-allocated, they will be freed 
> > way
> >  >>  before drm_mode_config_cleanup() is called. To avoid 
> > use-after-free
> >  >>  conditions, we then must ensure that drm_encoder_cleanup() is 
> > called
> >  >>  before the encoders are freed.
> >  >>
> >  >>  v2: Use the new __drmm_simple_encoder_alloc() function
> >  >>
> >  >>  Fixes: c369cb27c267 ("drm/ingenic: Support multiple 
> > panels/bridges")
> >  >>  Cc: <stable@xxxxxxxxxxxxxxx> # 5.8+
> >  >>  Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  >>  ---
> >  >>
> >  >>  Notes:
> >  >>      Use the V1 of this patch to fix v5.11 and older kernels. 
> > This
> >  >> V2 only
> >  >>      applies on the current drm-misc-next branch.
> >  >>
> >  >>   drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 16 +++++++---------
> >  >>   1 file changed, 7 insertions(+), 9 deletions(-)
> >  >>
> >  >>  diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> >  >> b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> >  >>  index 7bb31fbee29d..158433b4c084 100644
> >  >>  --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> >  >>  +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> >  >>  @@ -1014,20 +1014,18 @@ static int ingenic_drm_bind(struct 
> > device
> >  >> *dev, bool has_components)
> >  >>                          bridge =
> >  >> devm_drm_panel_bridge_add_typed(dev, panel,
> >  >>
> >  >> DRM_MODE_CONNECTOR_DPI);
> >  >>
> >  >>  -               encoder = devm_kzalloc(dev, sizeof(*encoder),
> >  >> GFP_KERNEL);
> >  >>  -               if (!encoder)
> >  >>  -                       return -ENOMEM;
> >  >>  +               encoder = __drmm_simple_encoder_alloc(drm,
> >  >> sizeof(*encoder), 0,
> >  >
> >  > Please don't use the __ prefixed functions, those are the internal
> >  > ones. The official one comes with type checking and all that 
> > included.
> >  > Otherwise lgtm.
> >  > -Daniel
> >
> >  The non-prefixed one assumes that I want to allocate a struct that
> >  contains the encoder, not just the drm_encoder itself.
>
> Hm, but using the internal one is also a bit too ugly. A
> drm_plain_simple_enocder_alloc(drm, type) wrapper would be the right
> thing here I think? Setting the offsets and struct sizes directly in
> these in drivers really doesn't feel like a good idea. I think simple
> encoder is the only case where we really have a need for a
> non-embeddable struct.
> -Daniel

Alright, I will add a wrapper.

Cheers,
-Paul

> >  >>  +
> >  >> DRM_MODE_ENCODER_DPI);
> >  >>  +               if (IS_ERR(encoder)) {
> >  >>  +                       ret = PTR_ERR(encoder);
> >  >>  +                       dev_err(dev, "Failed to init encoder:
> >  >> %d\n", ret);
> >  >>  +                       return ret;
> >  >>  +               }
> >  >>
> >  >>                  encoder->possible_crtcs = 1;
> >  >>
> >  >>                  drm_encoder_helper_add(encoder,
> >  >> &ingenic_drm_encoder_helper_funcs);
> >  >>
> >  >>  -               ret = drm_simple_encoder_init(drm, encoder,
> >  >> DRM_MODE_ENCODER_DPI);
> >  >>  -               if (ret) {
> >  >>  -                       dev_err(dev, "Failed to init encoder:
> >  >> %d\n", ret);
> >  >>  -                       return ret;
> >  >>  -               }
> >  >>  -
> >  >>                  ret = drm_bridge_attach(encoder, bridge, NULL, 
> > 0);
> >  >>                  if (ret) {
> >  >>                          dev_err(dev, "Unable to attach 
> > bridge\n");
> >  >>  --
> >  >>  2.29.2
> >  >>
> >  >
> >  >
> >  > --
> >  > Daniel Vetter
> >  > Software Engineer, Intel Corporation
> >  > http://blog.ffwll.ch
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch