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

2021-12-07 Thread George Kennedy

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.kenn...@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
 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:  [#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 

Reviewed-by: Geert Uytterhoeven 

Gr{oetje,eeting}s,

 Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-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




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

2021-10-28 Thread Geert Uytterhoeven
On Wed, Oct 27, 2021 at 10:32 PM George Kennedy
 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:  [#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 

Reviewed-by: Geert Uytterhoeven 

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-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