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drm/vc4: Use managed KMS polling to fix UAF on unbind

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vc4_kms_load() calls drm_kms_helper_poll_init() but the driver provides
no matching drm_kms_helper_poll_fini(). The output poll work stays
scheduled after unbind and runs on the freed drm_device:

  # modprobe vc4; rmmod vc4; sleep 10
  BUG: KASAN: slab-use-after-free in delayed_work_timer_fn
  BUG: KASAN: slab-use-after-free in drm_client_dev_hotplug [drm]
  Workqueue: events output_poll_execute [drm_kms_helper]
  Allocated by task 171: __devm_drm_dev_alloc
  Freed by task 262 (rmmod): drm_dev_put / component_del

Use drmm_kms_helper_poll_init() so polling is finalized with the device,
as other drivers do.

Fixes: c8b75bca92 ("drm/vc4: Add KMS support for Raspberry Pi.")
Assisted-by: Claude:claude-fable-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Link: https://patch.msgid.link/20260822143110.68594-1-kmehltretter@gmail.com
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
This commit is contained in:
Karl Mehltretter 2026-08-22 16:31:10 +02:00 committed by Maíra Canal
parent 59ced288fc
commit 073a30d75f
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1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/vc4/vc4_kms.c
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@ -1188,7 +1188,7 @@ int vc4_kms_load(struct drm_device *dev)
drm_mode_config_reset(dev);
drm_kms_helper_poll_init(dev);
drmm_kms_helper_poll_init(dev);
return 0;
}