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

[Nicolas Frattaroli]

On Friday, 17 October 2025 18:15:03 Central European Standard Time Luca Ceresoli wrote:
> 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@xxxxxxxxxxx/
> [2] https://lore.kernel.org/lkml/336fbfdd-c424-490e-b5d1-8ee84043dc80@xxxxxxxxxxx/
> [3] https://lore.kernel.org/lkml/CA+G9fYuKHp3QgPKjgFY3TfkDdh5Vf=Ae5pCW+eU41Bu=D7th2g@xxxxxxxxxxxxxx/
> [4] https://lore.kernel.org/lkml/20251016-drm-bridge-alloc-getput-bridge-connector-fix-hdmi_cec-v1-1-81d6984c5361@xxxxxxxxxxx/
> 
> Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxx
> 
> ---
> 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,
> 

Tested-by: Nicolas Frattaroli <nicolas.frattaroli@xxxxxxxxxxxxx>

Fixes a null pointer dereference on boot on my Radxa ROCK 5T
(RK3588) that's present in next-20251027.

Kind regards,
Nicolas Frattaroli