[PATCH v2] video: fbdev: kyro: fix a DoS bug by restricting user input

[Zheyu Ma]

On Tue, Jul 20, 2021 at 2:50 AM Sam Ravnborg <sam at ravnborg.org> wrote:
>
> Hi Zheyu,
> On Wed, Jul 14, 2021 at 04:09:22AM +0000, Zheyu Ma wrote:
> > The user can pass in any value to the driver through the 'ioctl'
> > interface. The driver dost not check, which may cause DoS bugs.
> >
> > The following log reveals it:
> >
> > divide error: 0000 [#1] PREEMPT SMP KASAN PTI
> > RIP: 0010:SetOverlayViewPort+0x133/0x5f0 drivers/video/fbdev/kyro/STG4000OverlayDevice.c:476
> > Call Trace:
> >  kyro_dev_overlay_viewport_set drivers/video/fbdev/kyro/fbdev.c:378 [inline]
> >  kyrofb_ioctl+0x2eb/0x330 drivers/video/fbdev/kyro/fbdev.c:603
> >  do_fb_ioctl+0x1f3/0x700 drivers/video/fbdev/core/fbmem.c:1171
> >  fb_ioctl+0xeb/0x130 drivers/video/fbdev/core/fbmem.c:1185
> >  vfs_ioctl fs/ioctl.c:48 [inline]
> >  __do_sys_ioctl fs/ioctl.c:753 [inline]
> >  __se_sys_ioctl fs/ioctl.c:739 [inline]
> >  __x64_sys_ioctl+0x19b/0x220 fs/ioctl.c:739
> >  do_syscall_64+0x32/0x80 arch/x86/entry/common.c:46
> >  entry_SYSCALL_64_after_hwframe+0x44/0xae
> >
> > Signed-off-by: Zheyu Ma <zheyuma97 at gmail.com>
> > ---
> > Changes in v2:
> >     - Validate the inputs on a higher level
>
> Much better, thanks.
> When a line is continued like here the statement shall aling with the
> opening brace. I fixed it up when applying the patch to drm-misc-next so
> no need to do anything this time.

Thanks for your kind reminder, I will pay attention next time.

Regards,
Zheyu Ma