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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Zheyu Ma <zheyuma97@gmail.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.14 183/432] video: fbdev: kyro: fix a DoS bug by restricting user input
Date:   Thu, 16 Sep 2021 17:58:52 +0200
Message-Id: <20210916155816.933160894@linuxfoundation.org>
In-Reply-To: <20210916155810.813340753@linuxfoundation.org>
References: <20210916155810.813340753@linuxfoundation.org>
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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