[PATCH] drivers/video/fbdev/core/fbmem.c: add pointer judgment

[Arnd Bergmann]

>  > On Wed, May 19, 2021 at 08:00:28PM +0800, songqiang wrote:
> > Signed-off-by: songqiang <songqiang at uniontech.com>
> From: "Matthew Wilcox <willy at infradead.org>"
> > You need to explain:
> >
> > - Why you think this patch is needed
> > - Did you observe a problem at runtime?
> > - Is this the output from some checking tool?
> > - Why this is the right way to address the problem
>
On Thu, May 20, 2021 at 7:58 AM 宋强 <songqiang at uniontech.com> wrote:
>
> I find null pointer bug when I debug the kernel of loongson，I think the function fb_set_suspend()
> add pointer judgment will more friendly.

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> [  102.011018] Call Trace:
>
> [  102.013443] [<ffffffff81068e10>] fb_set_suspend+0x50/0x80
> [  102.018819] [<ffffffffc0061aa0>] loongson_drm_suspend+0x1a0/0x340 [loongson]
> [  102.025827] [<ffffffffc0061c58>] loongson_pmops_freeze+0x18/0x40 [loongson]
> [  102.032748] [<ffffffff81008fd4>] pci_pm_freeze+0x94/0x240
> [  102.038114] [<ffffffff815377e0>] dpm_run_callback.isra.5+0x20/0x140
> [  102.044341] [<ffffffff81539608>] __device_suspend+0x2c8/0x740

It looks like the check would actually belong into the loongson_drm driver.
The driver is not upstream yet, but I assume you have the source for it, so
try to fix the bug there and send the patch to the owners of that driver.

       Arnd