From 9e7faff181ce4f60372114cb1df601d0f1629fab Mon Sep 17 00:00:00 2001
From: Tim Schumacher <timschumi@gmx.de>
Date: Fri, 19 Aug 2022 10:41:38 +0200
Subject: [PATCH] Kernel: Protect the list of unused network packets with a
 Spinlock

---
 Kernel/Net/NetworkAdapter.cpp | 32 ++++++++++++++++----------------
 Kernel/Net/NetworkAdapter.h   |  2 +-
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/Kernel/Net/NetworkAdapter.cpp b/Kernel/Net/NetworkAdapter.cpp
index a9d97bc5a7..4ba93ca6e0 100644
--- a/Kernel/Net/NetworkAdapter.cpp
+++ b/Kernel/Net/NetworkAdapter.cpp
@@ -113,21 +113,20 @@ size_t NetworkAdapter::dequeue_packet(u8* buffer, size_t buffer_size, Time& pack
 
 RefPtr<PacketWithTimestamp> NetworkAdapter::acquire_packet_buffer(size_t size)
 {
-    InterruptDisabler disabler;
-    if (m_unused_packets.is_empty()) {
-        auto buffer_or_error = KBuffer::try_create_with_size("NetworkAdapter: Packet buffer"sv, size, Memory::Region::Access::ReadWrite, AllocationStrategy::AllocateNow);
-        if (buffer_or_error.is_error())
-            return {};
-        auto buffer = buffer_or_error.release_value();
-        auto packet = adopt_ref_if_nonnull(new (nothrow) PacketWithTimestamp { move(buffer), kgettimeofday() });
-        if (!packet)
-            return {};
-        packet->buffer->set_size(size);
-        return packet;
-    }
+    auto packet = m_unused_packets.with([size](auto& unused_packets) -> RefPtr<PacketWithTimestamp> {
+        if (unused_packets.is_empty())
+            return nullptr;
 
-    auto packet = m_unused_packets.take_first();
-    if (packet->buffer->capacity() >= size) {
+        auto unused_packet = unused_packets.take_first();
+
+        if (unused_packet->buffer->capacity() >= size)
+            return unused_packet;
+
+        // FIXME: Shouldn't we put existing buffers that are too small back into the list?
+        return nullptr;
+    });
+
+    if (packet) {
         packet->timestamp = kgettimeofday();
         packet->buffer->set_size(size);
         return packet;
@@ -145,8 +144,9 @@ RefPtr<PacketWithTimestamp> NetworkAdapter::acquire_packet_buffer(size_t size)
 
 void NetworkAdapter::release_packet_buffer(PacketWithTimestamp& packet)
 {
-    InterruptDisabler disabler;
-    m_unused_packets.append(packet);
+    m_unused_packets.with([&packet](auto& unused_packets) {
+        unused_packets.append(packet);
+    });
 }
 
 void NetworkAdapter::set_ipv4_address(IPv4Address const& address)
diff --git a/Kernel/Net/NetworkAdapter.h b/Kernel/Net/NetworkAdapter.h
index 99c4ed6027..f2da877383 100644
--- a/Kernel/Net/NetworkAdapter.h
+++ b/Kernel/Net/NetworkAdapter.h
@@ -109,7 +109,7 @@ private:
 
     PacketList m_packet_queue;
     size_t m_packet_queue_size { 0 };
-    PacketList m_unused_packets;
+    SpinlockProtected<PacketList> m_unused_packets;
     NonnullOwnPtr<KString> m_name;
     u32 m_packets_in { 0 };
     u32 m_bytes_in { 0 };