linux-kernel - [PATCH v2 0/3] drm/display: bridge_connector: get/put the stored bridges: fix NULL pointer regression

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Message-Id: <20251017-drm-bridge-alloc-getput-bridge-connector-fix-hdmi_cec-v2-0-667abf6d47c0@bootlin.com>
Date: Fri, 17 Oct 2025 18:15:03 +0200
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Marek Szyprowski <m.szyprowski@...sung.com>, 
 Naresh Kamboju <naresh.kamboju@...aro.org>, 
 Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Hui Pu <Hui.Pu@...ealthcare.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH v2 0/3] drm/display: bridge_connector: get/put the stored
 bridges: fix NULL pointer regression

A patch of mine recently merged in drm-misc-next [1] has a NULL pointer
deref regression (reported here [2] and here [3]). Being in lack of a quick
fix, I sent a revert proposal [4].

The revert proposal has no answers currenty, and in the meanwhile I have a
patch that implements the original idea but without the same bug. So here's
a v2 series with:

 - the same revert patch
 - the original patch but rewritten without the same bug (and even simpler)

Also the re-written patch is now split in two for clarity because it was
doing two somewhat different things.

[1] https://lore.kernel.org/all/20250926-drm-bridge-alloc-getput-bridge-connector-v2-1-138b4bb70576@bootlin.com/
[2] https://lore.kernel.org/lkml/336fbfdd-c424-490e-b5d1-8ee84043dc80@samsung.com/
[3] https://lore.kernel.org/lkml/CA+G9fYuKHp3QgPKjgFY3TfkDdh5Vf=Ae5pCW+eU41Bu=D7th2g@mail.gmail.com/
[4] https://lore.kernel.org/lkml/20251016-drm-bridge-alloc-getput-bridge-connector-fix-hdmi_cec-v1-1-81d6984c5361@bootlin.com/

Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
---
Changes in v2:
- No changes to the revert patch
- Added the (corrected) patch introducing the same feature as the original
  buggy patch, and also split it in two fir clarity
- Link to v1: https://lore.kernel.org/r/20251016-drm-bridge-alloc-getput-bridge-connector-fix-hdmi_cec-v1-1-81d6984c5361@bootlin.com

---
Luca Ceresoli (3):
      Revert "drm/display: bridge_connector: get/put the stored bridges"
      drm/display: bridge_connector: get/put the stored bridges
      drm/display: bridge_connector: get/put the panel_bridge

 drivers/gpu/drm/display/drm_bridge_connector.c | 92 +++++++++++---------------
 1 file changed, 39 insertions(+), 53 deletions(-)
---
base-commit: 84a0a3f014cda68ff10b8517d09e9f0c1cd942a2
change-id: 20251016-drm-bridge-alloc-getput-bridge-connector-fix-hdmi_cec-9a429ddb48e2

Best regards,
-- 
Luca Ceresoli <luca.ceresoli@...tlin.com>