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Subject: drm: Possible NULL ptr exceptions in other DRM drivers
From: Krzysztof Kozlowski <k.kozlowski@samsung.com>
To: David Airlie <airlied@linux.ie>, Thomas Hellstrom <thellstrom@vmware.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Daniel Vetter <daniel.vetter@ffwll.ch>, BenSkeggs <bskeggs@redhat.com>,
        RobClark <robdclark@gmail.com>, GerdHoffmann <kraxel@redhat.com>
Date: Thu, 03 Jul 2014 10:33:54 +0200
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Hi,

In Exynos DRM driver I found a NULL pointer exception when there were no
components set for DRM driver:
https://lkml.org/lkml/2014/6/30/331

The NULL pointer will happen during driver suspend if drm_driver.load()
is not called. The load() won't be called if no components are added.

After looking at other DRM drivers it seems that they may also be
affected by this issue. Some possible candidates (for my amateur's eyes)
are:
1. vmwgfx/vmwgfx_drv.c (vmw_pci_suspend: dereference of 'dev_priv')
2. qxl/qxl_drv.c (qxl_drm_freeze: dereference of 'qdev')
3. nouveau/nouveau_drm.c (nouveau_do_suspend: dereference of 'drm')
4. msm/msm_drv.c (msm_pm_suspend: dereference of 'ddev')
5. cirrus/cirrus_drv.c (cirrus_pm_suspend: dereference of 'cdev')
6. bochs/bochs_drv.c (bochs_pm_suspend: dereference of 'bochs')

Unfortunately I am not familiar with DRM drivers and I do not have
hardware to test it.

Maybe it is worth looking at?

Best regards,
Krzysztof