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RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:mid,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -3.01 Hi Am 15.09.25 um 13:27 schrieb Maxime Ripard: > On Tue, Sep 02, 2025 at 03:18:17PM +0200, Thomas Zimmermann wrote: >> Hi >> >> Am 02.09.25 um 10:32 schrieb Maxime Ripard: >>> Bridges implement their state using a drm_private_obj and an >>> hand-crafted reset implementation. >>> >>> Since drm_private_obj doesn't have a set of reset helper like the other >>> states, __drm_atomic_helper_bridge_reset() was initializing both the >>> drm_private_state and the drm_bridge_state structures. >>> >>> This initialization however was missing the drm_private_state.obj >>> pointer to the drm_private_obj the state was allocated for, creating a >>> NULL pointer dereference when trying to access it. >>> >>> Fixes: 751465913f04 ("drm/bridge: Add a drm_bridge_state object") >>> Signed-off-by: Maxime Ripard >>> --- >>> drivers/gpu/drm/drm_atomic_state_helper.c | 8 ++++++++ >>> 1 file changed, 8 insertions(+) >>> >>> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c >>> index 7142e163e618ea0d7d9d828e1bd9ff2a6ec0dfeb..b962c342b16aabf4e3bea52a914e5deb1c2080ce 100644 >>> --- a/drivers/gpu/drm/drm_atomic_state_helper.c >>> +++ b/drivers/gpu/drm/drm_atomic_state_helper.c >>> @@ -707,10 +707,17 @@ void drm_atomic_helper_connector_destroy_state(struct drm_connector *connector, >>> __drm_atomic_helper_connector_destroy_state(state); >>> kfree(state); >>> } >>> EXPORT_SYMBOL(drm_atomic_helper_connector_destroy_state); >>> +static void __drm_atomic_helper_private_obj_reset(struct drm_private_obj *obj, >>> + struct drm_private_state *state) >>> +{ >>> + memset(state, 0, sizeof(*state)); >> This argument is guaranteed to be zero'd, I think. No need for a memset. >> >>> + state->obj = obj; >>> +} >>> + >>> /** >>> * __drm_atomic_helper_private_obj_duplicate_state - copy atomic private state >>> * @obj: CRTC object >>> * @state: new private object state >>> * >>> @@ -796,10 +803,11 @@ EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state); >>> */ >>> void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge, >>> struct drm_bridge_state *state) >>> { >>> memset(state, 0, sizeof(*state)); >> Another unnecessary memset? > I guess the two can be seen as redundant, but I'd argue the one in > __drm_atomic_helper_private_obj_reset should still be there. > > What guarantees that the pointer points to a zero'd structure? We only call this helper after allocation AFAICT. And the DRM APIs already assume that allocation clears to zero. Best regards Thomas > > Maxime -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)