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Message-ID: <elql7sqecqlik7shmgvpgnghgapzp5oe4mf4vlklx4ml6z5664@f5mw6g4fvjff>
Date: Wed, 10 Sep 2025 18:32:02 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: abhinav.kumar@...ux.dev, airlied@...il.com, alexander.deucher@....com,
amd-gfx@...ts.freedesktop.org, christian.koenig@....com,
dave.stevenson@...pberrypi.com, dri-devel@...ts.freedesktop.org,
freedreno@...ts.freedesktop.org, geert+renesas@...der.be,
harry.wentland@....com, jani.nikula@...ux.intel.com,
jessica.zhang@....qualcomm.com, kernel-list@...pberrypi.com,
kieran.bingham+renesas@...asonboard.com,
laurent.pinchart+renesas@...asonboard.com,
linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, liviu.dudau@....com,
louis.chauvet@...tlin.com, lumag@...nel.org,
maarten.lankhorst@...ux.intel.com, magnus.damm@...il.com,
marijn.suijten@...ainline.org, mcanal@...lia.com, mripard@...nel.org,
robin.clark@....qualcomm.com, sean@...rly.run, simona@...ll.ch,
siqueira@...lia.com, sunpeng.li@....com, suraj.kandpal@...el.com,
tomi.valkeinen+renesas@...asonboard.com, tzimmermann@...e.de
Subject: Re: [PATCH v3 4/8] drm/msm/dpu: use drmm_writeback_connector_init()
On Wed, Sep 10, 2025 at 07:32:51AM +0200, Christophe JAILLET wrote:
> Le 10/09/2025 à 05:47, Dmitry Baryshkov a écrit :
> > On Mon, Sep 08, 2025 at 11:38:44PM +0200, Christophe JAILLET wrote:
> > > Le 08/09/2025 à 23:26, Dmitry Baryshkov a écrit :
> > > > On Mon, Sep 08, 2025 at 11:09:07PM +0200, Christophe JAILLET wrote:
> > > > > Le 19/08/2025 à 22:32, Dmitry Baryshkov a écrit :
> > > > > > Use drmm_plain_encoder_alloc() to allocate simple encoder and
> > > > > > drmm_writeback_connector_init() in order to initialize writeback
> > > > > > connector instance.
> > > > > >
> > > > > > Reviewed-by: Louis Chauvet <louis.chauvet-LDxbnhwyfcJBDgjK7y7TUQ-XMD5yJDbdMReXY1tMh2IBg-XMD5yJDbdMReXY1tMh2IBg@...lic.gmane.org>
> > > > > > Reviewed-by: Suraj Kandpal <suraj.kandpal-ral2JQCrhuEAvxtiuMwx3w-XMD5yJDbdMReXY1tMh2IBg-XMD5yJDbdMReXY1tMh2IBg@...lic.gmane.org>
> > > > > > Reviewed-by: Jessica Zhang <jessica.zhang-5oFBVzJwu8Ry9aJCnZT0Uw-XMD5yJDbdMReXY1tMh2IBg-XMD5yJDbdMReXY1tMh2IBg@...lic.gmane.org>
> > > > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov-5oFBVzJwu8Ry9aJCnZT0Uw-XMD5yJDbdMReXY1tMh2IBg-XMD5yJDbdMReXY1tMh2IBg@...lic.gmane.org>
> > > > > > ---
> > > > > > drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c | 10 +++-------
> > > > > > 1 file changed, 3 insertions(+), 7 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
> > > > > > index 8ff496082902b1ee713e806140f39b4730ed256a..cd73468e369a93c50303db2a7d4499bcb17be5d1 100644
> > > > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
> > > > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
> > > > > > @@ -80,7 +80,6 @@ static int dpu_wb_conn_atomic_check(struct drm_connector *connector,
> > > > > > static const struct drm_connector_funcs dpu_wb_conn_funcs = {
> > > > > > .reset = drm_atomic_helper_connector_reset,
> > > > > > .fill_modes = drm_helper_probe_single_connector_modes,
> > > > > > - .destroy = drm_connector_cleanup,
> > > > > > .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> > > > > > .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> > > > > > };
> > > > > > @@ -131,12 +130,9 @@ int dpu_writeback_init(struct drm_device *dev, struct drm_encoder *enc,
> > > > > > drm_connector_helper_add(&dpu_wb_conn->base.base, &dpu_wb_conn_helper_funcs);
> > > > > > - /* DPU initializes the encoder and sets it up completely for writeback
> > > > > > - * cases and hence should use the new API drm_writeback_connector_init_with_encoder
> > > > > > - * to initialize the writeback connector
> > > > > > - */
> > > > > > - rc = drm_writeback_connector_init_with_encoder(dev, &dpu_wb_conn->base, enc,
> > > > > > - &dpu_wb_conn_funcs, format_list, num_formats);
> > > > > > + rc = drmm_writeback_connector_init(dev, &dpu_wb_conn->base,
> > > > > > + &dpu_wb_conn_funcs, enc,
> > > > > > + format_list, num_formats);
> > > > > > if (!rc)
> > > > > > dpu_wb_conn->wb_enc = enc;
> > > > > >
> > > > >
> > > > > dpu_wb_conn is allocated a few lines above using devm_kzalloc().
> > > >
> > > > That's a valid point, thanks!
> > >
> > > I've not analyzed in details all the patches of the serie, but at least
> > > patch 2/8 and 6/8 seems to have the same pattern.
> >
> > Not quite, 2/8 and 6/8 use drmm_kzalloc(), it is fine to be used with
> > drmm_writeback_connector_init(). This one is indeed incorrect.
> >
>
> Hmm, for patch 2/8, I looked at the source, not what was changes by your
> patch... Sorry. :(
>
> For 6/8, I agree with you.
>
> For patch 1/8, I think there is a issue too, becasue of [1], IIUC.
There is a different issue then. It's a memory leak inside the AMD
driver (since the memory for WB connector will not be kfree()'d by
anything).
>
> CJ
>
>
> [1]: https://elixir.bootlin.com/linux/v6.17-rc5/source/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c#L5257
>
> > >
> > > CJ
> > >
> > > >
> > > > >
> > > > > Based on [1], mixing devm_ and drmm_ is not safe and can lead to a uaf.
> > > > >
> > > > > Is it correct here?
> > > > > If the explanation at [1] is correct, then &dpu_wb_conn->base would point to
> > > > > some released memory, IIUC.
> > > > >
> > > > >
> > > > > just my 2c.
> > > > >
> > > > > CJ
> > > > >
> > > > > [1]: https://web.git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/gpu/drm/xe/xe_hwmon.c?id=3a13c2de442d6bfaef9c102cd1092e6cae22b753
> > > >
> > >
> >
>
--
With best wishes
Dmitry
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