Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
New issues: - [Critical] Replacing `pm_runtime_put()` with `pm_runtime_put_sync()` synchronously powers off the hardware before tearing down child devices, DRM bridges, and IRQs, causing system crashes when they access unpowered registers. Pre-existing issues: - [High] Using `timer_delete_sync()` instead of `timer_shutdown_sync()` in the remove path allows the timer to be re-armed by the concurrently active IRQ thread, leading to a use-after-free. -- --- Patch [3]: [PATCH v4 03/12] drm/mediatek: mtk_dp: Call pm_runtime_put_sync() in removal path --- commit f976047da5b8089ab1d0475df94302360f23d7f2 Author: AngeloGioacchino Del Regno <[email protected]> drm/mediatek: mtk_dp: Call pm_runtime_put_sync() in removal path Since pm_runtime_put() queues an asynchronous suspend, calling pm_runtime_disable() right after will cancel the pending suspend work. Call pm_runtime_put_sync() instead during mtk_dp_remove() to overcome to this issue, making sure that the suspend ops execute and that the hardware correctly powers off before module unload. > diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c > b/drivers/gpu/drm/mediatek/mtk_dp.c > index f656b85b84212..0d0507890d993 100644 > --- a/drivers/gpu/drm/mediatek/mtk_dp.c > +++ b/drivers/gpu/drm/mediatek/mtk_dp.c > @@ -2866,7 +2866,7 @@ static void mtk_dp_remove(struct platform_device *pdev) > { > struct mtk_dp *mtk_dp = platform_get_drvdata(pdev); > > - pm_runtime_put(&pdev->dev); > + pm_runtime_put_sync(&pdev->dev); [Severity: Critical] Does changing this to a synchronous put cause a regression where the hardware is powered off before child devices and IRQs are torn down? Because the driver uses a devm-managed IRQ, the interrupt can still fire and execute mtk_dp_hpd_event() which reads hardware registers: mtk_dp_hpd_event() { u32 irq_status = mtk_dp_swirq_get_clear(mtk_dp) | mtk_dp_hwirq_get_clear(mtk_dp); ... } Additionally, child platform devices like the audio codec are still active. If they are torn down later and trigger mtk_dp_audio_shutdown(), it also accesses hardware: mtk_dp_audio_shutdown() { mtk_dp_audio_mute(mtk_dp, true); ... } Will accessing these registers after the PM domain is synchronously powered down result in a bus fault or system crash? Should the PM operations be moved to the end of the teardown process after explicitly disabling IRQs and unregistering child devices? > pm_runtime_disable(&pdev->dev); > if (mtk_dp->data->bridge_type != DRM_MODE_CONNECTOR_eDP) > - timer_delete_sync(&mtk_dp->debounce_timer); > + timer_delete_sync(&mtk_dp->debounce_timer); [Severity: High] This is a pre-existing issue, but could this timer_delete_sync() result in a use-after-free? Since the hardware interrupt is managed by devres, it remains active throughout mtk_dp_remove(). If the IRQ thread is executing concurrently, it can unconditionally re-arm the timer: mtk_dp_hpd_event_thread() { ... mod_timer(&mtk_dp->debounce_timer, jiffies + msecs_to_jiffies(100) - 1); } If mod_timer() is called right after timer_delete_sync() finishes, the timer is successfully re-armed. Once mtk_dp_remove() returns, devres will free the mtk_dp structure. When the timer expires, won't it access freed memory? Should this be updated to use timer_shutdown_sync() instead to permanently prevent the timer from being re-armed? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=3
