[PATCH AUTOSEL 5.14 028/252] video: fbdev: kyro: fix a DoS bug by restricting user input

Sasha Levin
2021-09-09T11:43:29Z

From: Zheyu Ma <zheyuma97@gmail.com>

[ Upstream commit 98a65439172dc69cb16834e62e852afc2adb83ed ]

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@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1626235762-2590-1-git-send-email-zheyuma97@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/video/fbdev/kyro/fbdev.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/video/fbdev/kyro/fbdev.c b/drivers/video/fbdev/kyro/fbdev.c
index 8fbde92ae8b9..4b8c7c16b1df 100644
--- a/drivers/video/fbdev/kyro/fbdev.c
+++ b/drivers/video/fbdev/kyro/fbdev.c
@@ -372,6 +372,11 @@ static int kyro_dev_overlay_viewport_set(u32 x, u32 y, u32 ulWidth, u32 ulHeight
/* probably haven't called CreateOverlay yet */
return -EINVAL;

+ if (ulWidth == 0 || ulWidth == 0xffffffff ||
+ ulHeight == 0 || ulHeight == 0xffffffff ||
+ (x < 2 && ulWidth + 2 == 0))
+ return -EINVAL;
+
/* Stop Ramdac Output */
DisableRamdacOutput(deviceInfo.pSTGReg);

--
2.30.2