linux-kernel - Re: [PATCH v2] video: fbdev: cirrusfb: check pixclock to avoid divide by zero

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Date:   Tue, 7 Dec 2021 14:01:28 -0500
From:   George Kennedy <george.kennedy@...cle.com>
To:     DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sam Ravnborg <sam@...nborg.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v2] video: fbdev: cirrusfb: check pixclock to avoid divide
 by zero

Can the DRM maintainers accept this Reviewed by patch?

Links to the Reviewed by patch:

https://lkml.org/lkml/2021/10/27/982
https://lore.kernel.org/all/1635366613-22507-1-git-send-email-george.kennedy@oracle.com/ 


Thank you,
George


On 10/28/2021 4:05 AM, Geert Uytterhoeven wrote:
> On Wed, Oct 27, 2021 at 10:32 PM George Kennedy
> <george.kennedy@...cle.com> wrote:
>> Do a sanity check on pixclock value to avoid divide by zero.
>>
>> If the pixclock value is zero, the cirrusfb driver will round up
>> pixclock to get the derived frequency as close to maxclock as
>> possible.
>>
>> Syzkaller reported a divide error in cirrusfb_check_pixclock.
>>
>> divide error: 0000 [#1] SMP KASAN PTI
>> CPU: 0 PID: 14938 Comm: cirrusfb_test Not tainted 5.15.0-rc6 #1
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2
>> RIP: 0010:cirrusfb_check_var+0x6f1/0x1260
>>
>> Call Trace:
>>   fb_set_var+0x398/0xf90
>>   do_fb_ioctl+0x4b8/0x6f0
>>   fb_ioctl+0xeb/0x130
>>   __x64_sys_ioctl+0x19d/0x220
>>   do_syscall_64+0x3a/0x80
>>   entry_SYSCALL_64_after_hwframe+0x44/0xae
>>
>> Signed-off-by: George Kennedy <george.kennedy@...cle.com>
> Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>
> Gr{oetje,eeting}s,
>
>                          Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds