From caa3fe8c457cae8046d3d8e87311895eedbcd541 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Thu, 5 Jan 2023 22:39:09 +0100
Subject: [PATCH] MemoryManager: Add validate_userspace_string()

A bit crude, should be replaced by a strdup_from_user() helper to avoid touching userspace memory directly.
But it'll do for now.
---
 kernel/src/memory/MemoryManager.cpp | 17 +++++++++++++++++
 kernel/src/memory/MemoryManager.h   |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/kernel/src/memory/MemoryManager.cpp b/kernel/src/memory/MemoryManager.cpp
index 75014bae..9a834af2 100644
--- a/kernel/src/memory/MemoryManager.cpp
+++ b/kernel/src/memory/MemoryManager.cpp
@@ -347,6 +347,23 @@ namespace MemoryManager
         return false;
     }
 
+    // FIXME: Replace this with some kind of strdup_from_user() function.
+    bool validate_userspace_string(u64 address)
+    {
+        if (!validate_readable_page(address)) return false;
+
+        while (*(char*)address != 0)
+        {
+            address++;
+            if (address % ARCH_PAGE_SIZE)
+            {
+                if (!validate_readable_page(address)) return false;
+            }
+        }
+
+        return true;
+    }
+
     usize free()
     {
         return free_mem;
diff --git a/kernel/src/memory/MemoryManager.h b/kernel/src/memory/MemoryManager.h
index d22ed45c..b2f72a84 100644
--- a/kernel/src/memory/MemoryManager.h
+++ b/kernel/src/memory/MemoryManager.h
@@ -20,6 +20,8 @@ namespace MemoryManager
     bool validate_readable_page(u64 address);
     bool validate_writable_page(u64 address);
 
+    bool validate_userspace_string(u64 address);
+
     Result<void> map_frames_at(u64 virt, u64 phys, usize count, int flags);
 
     Result<u64> alloc_at(u64 virt, usize count, int flags);