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

Started by Zheyu Ma on Jul 20, 2021

open the first message on its own page

Message details and related content
On Tue, Jul 20, 2021 at 2:50 AM Sam Ravnborg [off-list ref] wrote:
Hi Zheyu,
On Wed, Jul 14, 2021 at 04:09:22AM +0000, Zheyu Ma wrote:
quoted
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 <redacted>
---
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
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