[PATCH 1/2] drm/exynos: fix null pointer dereference issue

[Inki Dae]

2014-11-23 0:28 GMT+09:00 Inki Dae <inki.dae at samsung.com>:
> 2014-11-21 23:41 GMT+09:00 Gustavo Padovan <gustavo at padovan.org>:
>> 2014-11-21 Inki Dae <inki.dae at samsung.com>:
>>
>>> On 2014년 11월 21일 08:12, Gustavo Padovan wrote:
>>> > 2014-11-13 Inki Dae <inki.dae at samsung.com>:
>>> >
>>> >> This patch fixes null pointer dereference issue incurred
>>> >> when ipp driver is enabled and Exynos drm driver is closed.
>>> >>
>>> >> Non kms driver should register its own sub driver to setup necessary
>>> >> resources, which is done by load(). So null pointer dereference
>>> >> occurs when ipp driver is enabled and Exynos drm driver is closed
>>> >> because ipp core device is registered after component_master_add_with_match
>>> >> call.
>>> >>
>>> >> This patch makes exynos_drm_device_subdrv_probe() to be called after all non
>>> >> kms drivers are registered.
>>> >
>>> > This patch is breaking exynos initialization, exynos_drm_device_subdrv_probe()
>>> > needs the drvdata but it is still NULL at this point which make the whole
>>> > exynos init fails. The drvdata is only set in exynos_drm_load() so we need
>>> > call exynos_drm_device_subdrv_probe() after that.
>>>
>>> There might be my missing point but with this patch,
>>> exynos_drm_device_subdrv_probe() will be called after exynos_drm_load()
>>> call because all kms drivers are probed before
>>> component_master_add_with_match call so exynos_drm_load() must be called
>>> by component_master_add_with_match function before
>>> exynos_drm_device_subdrv_probe call.
>>>
>>> So could you show me the error messages you faced with? There might be a
>>> corner case I missed.
>>
>> I've added some debug output to it. It fails on
>> exynos_drm_device_subdrv_probe() because the drvdata is NULL. I've added debug
>> output to exynos_drm_load() and as you can see it doesn't get called before
>> subdrv_probe(). I'm testing this on snow.
>>
>> [    1.767835] [drm] Initialized drm 1.1.0 20060810
>> [    1.771120] [drm:exynos_drm_init]
>> [    1.774774] [drm:exynos_drm_platform_probe]
>> [    1.778760] platform exynos-drm: Driver exynos-drm requests probe deferral
>> [    1.786178] platform 145b0000.dp-controller: Driver exynos-dp requests
>> probe deferral
>> [    1.794374] exynos-drm-ipp exynos-drm-ipp: drm ipp registered successfully.
>> [    1.800372] [drm:exynos_drm_device_subdrv_probe] dev   (null)
>>
>
> Still strange to me. I'd like to reproduce this error because it's
> impossible that exynos_drm_device_subdrv_probe is called without load
> call.
> even If error, this patch must be no problem so in this case, we would
> need check if there might be something we missed about component
> binding not this patch.

But it's better to call exynos_drm_device_subdrv_probe() in load()
like before because we should move all register codes of sub drivers
into init() for the meantime. So let's just revert it.

Thanks,
Inki Dae

> So can you let me know where the git repository is and which defconfig
> file did you tested?
>
> Thanks,
> Inki Dae
>
>>
>>         Gustavo
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/dri-devel