linux-kernel - Re: [BUG] video: fbdev: broadsheetfb: Possible null function pointers

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Date:   Thu, 26 Jul 2018 16:34:53 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     bai <baijiaju1990@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [BUG] video: fbdev: broadsheetfb: Possible null function
 pointers

On Thursday, July 26, 2018 10:17:44 PM bai wrote:
> In Linux-4.16, drivers/video/fbdev/broadsheetfb.c,
> 
> 158. static void broadsheet_mmio_send_cmdargs(...) {
>              ......
> 163.     par->board->mmio_write(...);
>              ......
> 166.     par->board->mmio_write(...);
> 167. }
> 
> For x86 kernel configuration, I find that there is no assignment of the 
> function pointer ".mmio_write" in the kernel code.
> So calling the function pointer in lines 163 and 166 may cause a null 
> pointer dereference.
> 
> In this file, there are many calls to this function pointer...

This is a platform driver and it won't be used on x86 (actually it is
used only by single ARM PXA board). The dependency for FB_BROADSHEET
in Kconfig file could be improved to i.e.

	depends on FB && (ARCH_PXA || COMPILE_TEST)

but there is no bug there.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics