From 9b14a8605a8ef4ab81141f7baff634d472912beb Mon Sep 17 00:00:00 2001
From: Gunnar Beutner <gbeutner@serenityos.org>
Date: Thu, 17 Jun 2021 19:29:49 +0200
Subject: Kernel: Add a VERIFY() to make sure our DMA address is valid

This checks whether the address we're trying to use for DMA is low
enough so as not to overflow the I/O register.
---
 Kernel/Devices/SB16.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Kernel/Devices/SB16.cpp b/Kernel/Devices/SB16.cpp
index ec29fe28b0..83b3c20289 100644
--- a/Kernel/Devices/SB16.cpp
+++ b/Kernel/Devices/SB16.cpp
@@ -200,6 +200,9 @@ void SB16::dma_start(uint32_t length)
 
     // Write the buffer
     IO::out8(0x8b, addr >> 16);
+    auto page_number = addr >> 16;
+    VERIFY(page_number <= NumericLimits<u8>::max());
+    IO::out8(0x8b, page_number);
 
     // Enable the DMA channel
     IO::out8(0xd4, (channel % 4));
-- 
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