Kernel: Quickly reject userspace addresses in kernel_region_from_vaddr()

This avoids taking and releasing the MM lock just to reject an address
that we can tell from just looking at it that it won't ever be in the
kernel regions tree.

1 files changed, 3 insertions, 0 deletions

diff --git a/Kernel/Memory/MemoryManager.cpp b/Kernel/Memory/MemoryManager.cpp
index 07eb097970..d76a802ed0 100644
--- a/Kernel/Memory/MemoryManager.cpp
+++ b/Kernel/Memory/MemoryManager.cpp
@@ -645,6 +645,9 @@ UNMAP_AFTER_INIT void MemoryManager::initialize(u32 cpu)
 
 Region* MemoryManager::kernel_region_from_vaddr(VirtualAddress vaddr)
 {
+    if (is_user_address(vaddr))
+        return nullptr;
+
     SpinlockLocker lock(s_mm_lock);
     auto* region = MM.m_kernel_regions.find_largest_not_above(vaddr.get());
     if (!region || !region->contains(vaddr))