Kernel: Make the Jails' internal design a lot more sane

This is done with 2 major steps:
1. Remove JailManagement singleton and use a structure that resembles
    what we have with the Process object. This is required later for the
    second step in this commit, but on its own, is a major change that
    removes this clunky singleton that had no real usage by itself.
2. Use IntrusiveLists to keep references to Process objects in the same
    Jail so it will be much more straightforward to iterate on this kind
    of objects when needed. Previously we locked the entire Process list
    and we did a simple pointer comparison to check if the checked
    Process we iterate on is in the same Jail or not, which required
    taking multiple Spinlocks in a very clumsy and heavyweight way.

Kernel/Arch/aarch64/init.cpp

@@ -26,7 +26,6 @@
 #include <Kernel/Devices/DeviceManagement.h>
 #include <Kernel/FileSystem/VirtualFileSystem.h>
 #include <Kernel/Graphics/Console/BootFramebufferConsole.h>
-#include <Kernel/JailManagement.h>
 #include <Kernel/KSyms.h>
 #include <Kernel/Memory/MemoryManager.h>
 #include <Kernel/Panic.h>
@@ -175,8 +174,6 @@ extern "C" [[noreturn]] void init()
     Processor::disable_interrupts();
     TimeManagement::initialize(0);
 
-    JailManagement::the();
-
     Process::initialize();
     Scheduler::initialize();
 

Kernel/Arch/x86_64/init.cpp

@@ -38,7 +38,6 @@
 #include <Kernel/Graphics/Console/VGATextModeConsole.h>
 #include <Kernel/Graphics/GraphicsManagement.h>
 #include <Kernel/Heap/kmalloc.h>
-#include <Kernel/JailManagement.h>
 #include <Kernel/KSyms.h>
 #include <Kernel/Memory/MemoryManager.h>
 #include <Kernel/Multiboot.h>
@@ -231,7 +230,6 @@ extern "C" [[noreturn]] UNMAP_AFTER_INIT void init(BootInfo const& boot_info)
 
     __stack_chk_guard = get_fast_random<uintptr_t>();
 
-    JailManagement::the();
     Process::initialize();
 
     Scheduler::initialize();

Kernel/CMakeLists.txt

@@ -93,7 +93,6 @@ set(KERNEL_SOURCES
     Graphics/VirtIOGPU/GraphicsAdapter.cpp
     IOWindow.cpp
     Jail.cpp
-    JailManagement.cpp
     SanCov.cpp
     Storage/ATA/AHCI/Controller.cpp
     Storage/ATA/AHCI/Port.cpp
@@ -256,6 +255,7 @@ set(KERNEL_SOURCES
     PerformanceEventBuffer.cpp
     Process.cpp
     ProcessGroup.cpp
+    ProcessList.cpp
     Random.cpp
     Scheduler.cpp
     ScopedCritical.cpp

Kernel/FileSystem/SysFS/Subsystems/Kernel/Jails.cpp

@@ -1,12 +1,12 @@
 /*
- * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ * Copyright (c) 2022-2023, Liav A. <liavalb@hotmail.co.il>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include <AK/JsonObjectSerializer.h>
 #include <Kernel/FileSystem/SysFS/Subsystems/Kernel/Jails.h>
-#include <Kernel/JailManagement.h>
+#include <Kernel/Jail.h>
 #include <Kernel/Sections.h>
 
 namespace Kernel {
@@ -24,7 +24,7 @@ UNMAP_AFTER_INIT NonnullLockRefPtr<SysFSJails> SysFSJails::must_create(SysFSDire
 ErrorOr<void> SysFSJails::try_generate(KBufferBuilder& builder)
 {
     auto array = TRY(JsonArraySerializer<>::try_create(builder));
-    TRY(JailManagement::the().for_each_in_same_jail([&array](Jail& jail) -> ErrorOr<void> {
+    TRY(Jail::for_each_when_process_is_not_jailed([&array](Jail const& jail) -> ErrorOr<void> {
         auto obj = TRY(array.add_object());
         TRY(obj.add("index"sv, jail.index().value()));
         TRY(obj.add("name"sv, jail.name()));

Kernel/Jail.cpp

@@ -1,21 +1,70 @@
 /*
- * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ * Copyright (c) 2022-2023, Liav A. <liavalb@hotmail.co.il>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/IntrusiveList.h>
+#include <AK/Singleton.h>
 #include <Kernel/Jail.h>
+#include <Kernel/Process.h>
 
 namespace Kernel {
 
-ErrorOr<NonnullLockRefPtr<Jail>> Jail::create(Badge<JailManagement>, NonnullOwnPtr<KString> name, JailIndex index)
+static Atomic<u64> s_jail_id;
+static Singleton<SpinlockProtected<Jail::List, LockRank::None>> s_all_instances {};
+
+static JailIndex generate_jail_id()
 {
-    return adopt_nonnull_lock_ref_or_enomem(new (nothrow) Jail(move(name), index));
+    return s_jail_id.fetch_add(1);
 }
 
-Jail::Jail(NonnullOwnPtr<KString> name, JailIndex index)
+NonnullRefPtr<ProcessList> Jail::process_list()
+{
+    return m_process_list;
+}
+
+ErrorOr<NonnullLockRefPtr<Jail>> Jail::create(NonnullOwnPtr<KString> name)
+{
+    return s_all_instances->with([&](auto& list) -> ErrorOr<NonnullLockRefPtr<Jail>> {
+        auto process_list = TRY(ProcessList::create());
+        auto jail = TRY(adopt_nonnull_lock_ref_or_enomem(new (nothrow) Jail(move(name), generate_jail_id(), move(process_list))));
+        list.append(jail);
+        return jail;
+    });
+}
+
+ErrorOr<void> Jail::for_each_when_process_is_not_jailed(Function<ErrorOr<void>(Jail const&)> callback)
+{
+    return Process::current().jail().with([&](auto const& my_jail) -> ErrorOr<void> {
+        // Note: If we are in a jail, don't reveal anything about the outside world,
+        // not even the fact that we are in which jail...
+        if (my_jail)
+            return {};
+        return s_all_instances->with([&](auto& list) -> ErrorOr<void> {
+            for (auto& jail : list) {
+                TRY(callback(jail));
+            }
+            return {};
+        });
+    });
+}
+
+LockRefPtr<Jail> Jail::find_by_index(JailIndex index)
+{
+    return s_all_instances->with([&](auto& list) -> LockRefPtr<Jail> {
+        for (auto& jail : list) {
+            if (jail.index() == index)
+                return jail;
+        }
+        return {};
+    });
+}
+
+Jail::Jail(NonnullOwnPtr<KString> name, JailIndex index, NonnullRefPtr<ProcessList> process_list)
     : m_name(move(name))
     , m_index(index)
+    , m_process_list(move(process_list))
 {
 }
 
@@ -26,7 +75,7 @@ void Jail::detach(Badge<Process>)
         VERIFY(my_attach_count > 0);
         my_attach_count--;
         if (my_attach_count == 0) {
-            m_jail_list_node.remove();
+            m_list_node.remove();
         }
     });
 }

Kernel/Jail.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ * Copyright (c) 2022-2023, Liav A. <liavalb@hotmail.co.il>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -9,6 +9,7 @@
 #include <AK/DistinctNumeric.h>
 #include <AK/Error.h>
 #include <AK/IntrusiveList.h>
+#include <AK/IntrusiveListRelaxedConst.h>
 #include <AK/OwnPtr.h>
 #include <AK/RefPtr.h>
 #include <AK/Try.h>
@@ -16,19 +17,21 @@
 #include <Kernel/KString.h>
 #include <Kernel/Library/LockRefPtr.h>
 #include <Kernel/Locking/SpinlockProtected.h>
-#include <Kernel/Process.h>
 
 namespace Kernel {
 
-class JailManagement;
+class ProcessList;
 
 AK_TYPEDEF_DISTINCT_ORDERED_ID(u64, JailIndex);
 
 class Jail : public RefCounted<Jail> {
-    friend class JailManagement;
 
 public:
-    static ErrorOr<NonnullLockRefPtr<Jail>> create(Badge<JailManagement>, NonnullOwnPtr<KString>, JailIndex);
+    NonnullRefPtr<ProcessList> process_list();
+
+    static LockRefPtr<Jail> find_by_index(JailIndex);
+    static ErrorOr<NonnullLockRefPtr<Jail>> create(NonnullOwnPtr<KString> name);
+    static ErrorOr<void> for_each_when_process_is_not_jailed(Function<ErrorOr<void>(Jail const&)> callback);
 
     StringView name() const { return m_name->view(); }
     JailIndex index() const { return m_index; }
@@ -37,12 +40,19 @@ public:
     SpinlockProtected<size_t, LockRank::None>& attach_count() { return m_attach_count; }
 
 private:
-    Jail(NonnullOwnPtr<KString>, JailIndex);
+    Jail(NonnullOwnPtr<KString>, JailIndex, NonnullRefPtr<ProcessList>);
 
     NonnullOwnPtr<KString> m_name;
     JailIndex const m_index;
 
-    IntrusiveListNode<Jail, NonnullLockRefPtr<Jail>> m_jail_list_node;
+    IntrusiveListNode<Jail, NonnullLockRefPtr<Jail>> m_list_node;
+
+public:
+    using List = IntrusiveListRelaxedConst<&Jail::m_list_node>;
+
+private:
+    NonnullRefPtr<ProcessList> m_process_list;
+
     SpinlockProtected<size_t, LockRank::None> m_attach_count { 0 };
 };
 

Kernel/JailManagement.cpp

@@ -1,76 +0,0 @@
-/*
- * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#include <AK/Singleton.h>
-#include <Kernel/JailManagement.h>
-#include <Kernel/Process.h>
-#include <Kernel/Sections.h>
-
-namespace Kernel {
-
-static Singleton<JailManagement> s_the;
-static Atomic<u64> s_jail_id;
-
-UNMAP_AFTER_INIT JailManagement::JailManagement() = default;
-
-JailIndex JailManagement::generate_jail_id()
-{
-    return s_jail_id.fetch_add(1);
-}
-
-JailManagement& JailManagement::the()
-{
-    return *s_the;
-}
-
-LockRefPtr<Jail> JailManagement::find_jail_by_index(JailIndex index)
-{
-    return m_jails.with([&](auto& list) -> LockRefPtr<Jail> {
-        for (auto& jail : list) {
-            if (jail.index() == index)
-                return jail;
-        }
-        return {};
-    });
-}
-
-ErrorOr<void> JailManagement::for_each_in_same_jail(Function<ErrorOr<void>(Jail&)> callback)
-{
-    return Process::current().jail().with([&](auto const& my_jail) -> ErrorOr<void> {
-        // Note: If we are in a jail, don't reveal anything about the outside world,
-        // not even the fact that we are in which jail...
-        if (my_jail)
-            return {};
-        return m_jails.with([&](auto& list) -> ErrorOr<void> {
-            for (auto& jail : list) {
-                TRY(callback(jail));
-            }
-            return {};
-        });
-    });
-}
-
-LockRefPtr<Jail> JailManagement::find_first_jail_by_name(StringView name)
-{
-    return m_jails.with([&](auto& list) -> LockRefPtr<Jail> {
-        for (auto& jail : list) {
-            if (jail.name() == name)
-                return jail;
-        }
-        return {};
-    });
-}
-
-ErrorOr<NonnullLockRefPtr<Jail>> JailManagement::create_jail(NonnullOwnPtr<KString> name)
-{
-    return m_jails.with([&](auto& list) -> ErrorOr<NonnullLockRefPtr<Jail>> {
-        auto jail = TRY(Jail::create({}, move(name), generate_jail_id()));
-        list.append(jail);
-        return jail;
-    });
-}
-
-}

Kernel/JailManagement.h

@@ -1,42 +0,0 @@
-/*
- * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#pragma once
-
-#include <AK/DistinctNumeric.h>
-#include <AK/Error.h>
-#include <AK/IntrusiveList.h>
-#include <AK/OwnPtr.h>
-#include <AK/RefPtr.h>
-#include <AK/Try.h>
-#include <AK/Types.h>
-#include <Kernel/Jail.h>
-#include <Kernel/KString.h>
-#include <Kernel/Library/LockRefPtr.h>
-#include <Kernel/Locking/SpinlockProtected.h>
-
-namespace Kernel {
-
-class JailManagement {
-
-public:
-    JailManagement();
-    static JailManagement& the();
-
-    LockRefPtr<Jail> find_jail_by_index(JailIndex);
-    LockRefPtr<Jail> find_first_jail_by_name(StringView);
-
-    ErrorOr<NonnullLockRefPtr<Jail>> create_jail(NonnullOwnPtr<KString> name);
-
-    ErrorOr<void> for_each_in_same_jail(Function<ErrorOr<void>(Jail&)>);
-
-private:
-    JailIndex generate_jail_id();
-
-    SpinlockProtected<IntrusiveList<&Jail::m_jail_list_node>, LockRank::None> m_jails {};
-};
-
-}

Kernel/Process.cpp

@@ -48,7 +48,7 @@ extern ProcessID g_init_pid;
 
 RecursiveSpinlock<LockRank::None> g_profiling_lock {};
 static Atomic<pid_t> next_pid;
-static Singleton<SpinlockProtected<Process::List, LockRank::None>> s_all_instances;
+static Singleton<SpinlockProtected<Process::AllProcessesList, LockRank::None>> s_all_instances;
 READONLY_AFTER_INIT Memory::Region* g_signal_trampoline_region;
 
 static Singleton<MutexProtected<OwnPtr<KString>>> s_hostname;
@@ -58,98 +58,89 @@ MutexProtected<OwnPtr<KString>>& hostname()
     return *s_hostname;
 }
 
-SpinlockProtected<Process::List, LockRank::None>& Process::all_instances()
+SpinlockProtected<Process::AllProcessesList, LockRank::None>& Process::all_instances()
 {
     return *s_all_instances;
 }
 
 ErrorOr<void> Process::for_each_in_same_jail(Function<ErrorOr<void>(Process&)> callback)
 {
+    return Process::current().m_jail_process_list.with([&](auto const& list_ptr) -> ErrorOr<void> {
         ErrorOr<void> result {};
-    Process::all_instances().with([&](auto const& list) {
-        Process::current().jail().with([&](auto const& my_jail) {
+        if (list_ptr) {
+            list_ptr->attached_processes().with([&](auto const& list) {
                 for (auto& process : list) {
-                if (!my_jail) {
                     result = callback(process);
-                } else {
-                    // Note: Don't acquire the process jail spinlock twice if it's the same process
-                    // we are currently inspecting.
-                    if (&Process::current() == &process) {
-                        result = callback(process);
-                    } else {
-                        process.jail().with([&](auto const& their_jail) {
-                            if (their_jail.ptr() == my_jail.ptr())
-                                result = callback(process);
-                        });
-                    }
-                }
                     if (result.is_error())
                         break;
                 }
             });
+            return result;
+        }
+        all_instances().with([&](auto const& list) {
+            for (auto& process : list) {
+                result = callback(process);
+                if (result.is_error())
+                    break;
+            }
         });
         return result;
+    });
 }
 
 ErrorOr<void> Process::for_each_child_in_same_jail(Function<ErrorOr<void>(Process&)> callback)
 {
     ProcessID my_pid = pid();
+    return m_jail_process_list.with([&](auto const& list_ptr) -> ErrorOr<void> {
         ErrorOr<void> result {};
-    Process::all_instances().with([&](auto const& list) {
-        jail().with([&](auto const& my_jail) {
+        if (list_ptr) {
+            list_ptr->attached_processes().with([&](auto const& list) {
                 for (auto& process : list) {
-                if (!my_jail) {
                     if (process.ppid() == my_pid || process.has_tracee_thread(pid()))
                         result = callback(process);
-                } else {
-                    // FIXME: Is it possible to have a child process being pointing to itself
-                    // as the parent process under normal conditions?
-                    // Note: Don't acquire the process jail spinlock twice if it's the same process
-                    // we are currently inspecting.
-                    if (&Process::current() == &process && (process.ppid() == my_pid || process.has_tracee_thread(pid()))) {
-                        result = callback(process);
-                    } else {
-                        process.jail().with([&](auto const& their_jail) {
-                            if ((their_jail.ptr() == my_jail.ptr()) && (process.ppid() == my_pid || process.has_tracee_thread(pid())))
-                                result = callback(process);
-                        });
-                    }
-                }
                     if (result.is_error())
                         break;
                 }
             });
+            return result;
+        }
+        all_instances().with([&](auto const& list) {
+            for (auto& process : list) {
+                if (process.ppid() == my_pid || process.has_tracee_thread(pid()))
+                    result = callback(process);
+                if (result.is_error())
+                    break;
+            }
         });
         return result;
+    });
 }
 
 ErrorOr<void> Process::for_each_in_pgrp_in_same_jail(ProcessGroupID pgid, Function<ErrorOr<void>(Process&)> callback)
 {
+    return m_jail_process_list.with([&](auto const& list_ptr) -> ErrorOr<void> {
         ErrorOr<void> result {};
-    Process::all_instances().with([&](auto const& list) {
-        jail().with([&](auto const& my_jail) {
+        if (list_ptr) {
+            list_ptr->attached_processes().with([&](auto const& list) {
                 for (auto& process : list) {
-                if (!my_jail) {
                     if (!process.is_dead() && process.pgid() == pgid)
                         result = callback(process);
-                } else {
-                    // Note: Don't acquire the process jail spinlock twice if it's the same process
-                    // we are currently inspecting.
-                    if (&Process::current() == &process && !process.is_dead() && process.pgid() == pgid) {
-                        result = callback(process);
-                    } else {
-                        process.jail().with([&](auto const& their_jail) {
-                            if ((their_jail.ptr() == my_jail.ptr()) && !process.is_dead() && process.pgid() == pgid)
-                                result = callback(process);
-                        });
-                    }
-                }
                     if (result.is_error())
                         break;
                 }
             });
+            return result;
+        }
+        all_instances().with([&](auto const& list) {
+            for (auto& process : list) {
+                if (!process.is_dead() && process.pgid() == pgid)
+                    result = callback(process);
+                if (result.is_error())
+                    break;
+            }
         });
         return result;
+    });
 }
 
 ProcessID Process::allocate_pid()
@@ -502,23 +493,21 @@ void Process::crash(int signal, Optional<RegisterState const&> regs, bool out_of
 
 LockRefPtr<Process> Process::from_pid_in_same_jail(ProcessID pid)
 {
-    return Process::current().jail().with([&](auto const& my_jail) -> LockRefPtr<Process> {
-        return all_instances().with([&](auto const& list) -> LockRefPtr<Process> {
-            if (!my_jail) {
+    return Process::current().m_jail_process_list.with([&](auto const& list_ptr) -> LockRefPtr<Process> {
+        if (list_ptr) {
+            return list_ptr->attached_processes().with([&](auto const& list) -> LockRefPtr<Process> {
                 for (auto& process : list) {
                     if (process.pid() == pid) {
                         return process;
                     }
                 }
-            } else {
-                for (auto& process : list) {
-                    if (process.pid() == pid) {
-                        return process.jail().with([&](auto const& other_process_jail) -> LockRefPtr<Process> {
-                            if (other_process_jail.ptr() == my_jail.ptr())
-                                return process;
                 return {};
             });
         }
+        return all_instances().with([&](auto const& list) -> LockRefPtr<Process> {
+            for (auto& process : list) {
+                if (process.pid() == pid) {
+                    return process;
                 }
             }
             return {};
@@ -773,6 +762,13 @@ void Process::finalize()
     m_fds.with_exclusive([](auto& fds) { fds.clear(); });
     m_tty = nullptr;
     m_executable.with([](auto& executable) { executable = nullptr; });
+    m_jail_process_list.with([this](auto& list_ptr) {
+        if (list_ptr) {
+            list_ptr->attached_processes().with([&](auto& list) {
+                list.remove(*this);
+            });
+        }
+    });
     m_attached_jail.with([](auto& jail) {
         if (jail)
             jail->detach({});

Kernel/Process.h

@@ -104,6 +104,8 @@ static_assert(sizeof(GlobalFutexKey) == (sizeof(FlatPtr) * 2));
 
 struct LoadResult;
 
+class ProcessList;
+
 class Process final
     : public ListedRefCounted<Process, LockType::Spinlock>
     , public LockWeakable<Process> {
@@ -665,8 +667,6 @@ private:
         return nullptr;
     }
 
-    IntrusiveListNode<Process> m_list_node;
-
     SpinlockProtected<NonnullOwnPtr<KString>, LockRank::None> m_name;
 
     SpinlockProtected<OwnPtr<Memory::AddressSpace>, LockRank::None> m_space;
@@ -852,7 +852,15 @@ private:
 
     LockWeakPtr<Memory::Region> m_master_tls_region;
 
-    IntrusiveListNode<Process> m_jail_list_node;
+    IntrusiveListNode<Process> m_jail_process_list_node;
+    IntrusiveListNode<Process> m_all_processes_list_node;
+
+public:
+    using AllProcessesList = IntrusiveListRelaxedConst<&Process::m_all_processes_list_node>;
+    using JailProcessList = IntrusiveListRelaxedConst<&Process::m_jail_process_list_node>;
+
+private:
+    SpinlockProtected<RefPtr<ProcessList>, LockRank::None> m_jail_process_list;
     SpinlockProtected<RefPtr<Jail>, LockRank::Process> m_attached_jail {};
 
     size_t m_master_tls_size { 0 };
@@ -895,8 +903,18 @@ private:
     u8 m_protected_values_padding[PAGE_SIZE - sizeof(ProtectedValues)];
 
 public:
-    using List = IntrusiveListRelaxedConst<&Process::m_list_node>;
-    static SpinlockProtected<Process::List, LockRank::None>& all_instances();
+    static SpinlockProtected<Process::AllProcessesList, LockRank::None>& all_instances();
+};
+
+class ProcessList : public RefCounted<ProcessList> {
+public:
+    static ErrorOr<NonnullRefPtr<ProcessList>> create();
+    SpinlockProtected<Process::JailProcessList, LockRank::None>& attached_processes() { return m_attached_processes; }
+    SpinlockProtected<Process::JailProcessList, LockRank::None> const& attached_processes() const { return m_attached_processes; }
+
+private:
+    ProcessList() = default;
+    SpinlockProtected<Process::JailProcessList, LockRank::None> m_attached_processes;
 };
 
 // Note: Process object should be 2 pages of 4096 bytes each.

Kernel/ProcessList.cpp

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2023, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Process.h>
+
+namespace Kernel {
+
+ErrorOr<NonnullRefPtr<ProcessList>> ProcessList::create()
+{
+    return adopt_nonnull_ref_or_enomem(new (nothrow) ProcessList());
+}
+
+}

Kernel/Syscalls/execve.cpp

@@ -516,6 +516,7 @@ ErrorOr<void> Process::do_exec(NonnullRefPtr<OpenFileDescription> main_program_d
     auto old_credentials = this->credentials();
     auto new_credentials = old_credentials;
     auto old_process_attached_jail = m_attached_jail.with([&](auto& jail) -> RefPtr<Jail> { return jail; });
+    auto old_scoped_list = m_jail_process_list.with([&](auto& list) -> RefPtr<ProcessList> { return list; });
 
     bool executable_is_setid = false;
 
@@ -578,6 +579,11 @@ ErrorOr<void> Process::do_exec(NonnullRefPtr<OpenFileDescription> main_program_d
     m_attached_jail.with([&](auto& jail) {
         jail = old_process_attached_jail;
     });
+
+    m_jail_process_list.with([&](auto& list) {
+        list = old_scoped_list;
+    });
+
     m_environment = move(environment);
 
     TRY(m_unveil_data.with([&](auto& unveil_data) -> ErrorOr<void> {

Kernel/Syscalls/fork.cpp

@@ -70,6 +70,26 @@ ErrorOr<FlatPtr> Process::sys$fork(RegisterState& regs)
         return {};
     }));
 
+    ArmedScopeGuard remove_from_jail_process_list = [&]() {
+        m_jail_process_list.with([&](auto& list_ptr) {
+            if (list_ptr) {
+                list_ptr->attached_processes().with([&](auto& list) {
+                    list.remove(*child);
+                });
+            }
+        });
+    };
+    m_jail_process_list.with([&](auto& list_ptr) {
+        if (list_ptr) {
+            child->m_jail_process_list.with([&](auto& child_list_ptr) {
+                child_list_ptr = list_ptr;
+            });
+            list_ptr->attached_processes().with([&](auto& list) {
+                list.append(child);
+            });
+        }
+    });
+
     TRY(child->m_fds.with_exclusive([&](auto& child_fds) {
         return m_fds.with_exclusive([&](auto& parent_fds) {
             return child_fds.try_clone(parent_fds);
@@ -150,6 +170,7 @@ ErrorOr<FlatPtr> Process::sys$fork(RegisterState& regs)
     }));
 
     thread_finalizer_guard.disarm();
+    remove_from_jail_process_list.disarm();
 
     Process::register_new(*child);
 

Kernel/Syscalls/jail.cpp

@@ -7,7 +7,6 @@
 #include <AK/Userspace.h>
 #include <Kernel/API/Ioctl.h>
 #include <Kernel/Jail.h>
-#include <Kernel/JailManagement.h>
 #include <Kernel/Process.h>
 #include <Kernel/StdLib.h>
 
@@ -31,7 +30,7 @@ ErrorOr<FlatPtr> Process::sys$jail_create(Userspace<Syscall::SC_jail_create_para
         // any info leak about the "outside world" jail metadata.
         if (my_jail)
             return Error::from_errno(EPERM);
-        auto jail = TRY(JailManagement::the().create_jail(move(jail_name)));
+        auto jail = TRY(Jail::create(move(jail_name)));
         return jail->index().value();
     }));
     // Note: We do the copy_to_user outside of the m_attached_jail Spinlock locked scope because
@@ -64,13 +63,21 @@ ErrorOr<FlatPtr> Process::sys$jail_attach(Userspace<Syscall::SC_jail_attach_para
         // in the system, just return EPERM before doing anything else.
         if (my_jail)
             return EPERM;
-        auto jail = JailManagement::the().find_jail_by_index(static_cast<JailIndex>(params.index));
+        auto jail = Jail::find_by_index(static_cast<JailIndex>(params.index));
         if (!jail)
             return EINVAL;
         my_jail = *jail;
         my_jail->attach_count().with([&](auto& attach_count) {
             attach_count++;
         });
+        m_jail_process_list.with([&](auto& list_ptr) {
+            list_ptr = my_jail->process_list();
+            if (list_ptr) {
+                list_ptr->attached_processes().with([&](auto& list) {
+                    list.append(*this);
+                });
+            }
+        });
         return 0;
     });
 }