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Kernel: Make Process creation APIs OOM safe

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This change looks more involved than it actually is. This simply
reshuffles the previous Process constructor and splits out the
parts which can fail (resource allocation) into separate methods
which can be called from a factory method. The factory is then
used everywhere instead of the constructor.
This commit is contained in:
Brian Gianforcaro 2021-05-14 04:55:43 -07:00 committed by Andreas Kling
parent 77868abe6a
commit ede1483e48
Notes: sideshowbarker 2024-07-18 18:07:29 +09:00 
Author: https://github.com/bgianfo
Commit: https://github.com/SerenityOS/serenity/commit/ede1483e48a
Pull-request: https://github.com/SerenityOS/serenity/pull/7103
Reviewed-by: https://github.com/awesomekling
3 changed files with 30 additions and 8 deletions
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30
Kernel/Process.cpp
View File

@ -144,7 +144,7 @@ RefPtr<Process> Process::create_user_process(RefPtr<Thread>& first_thread, const
if (!cwd)
cwd = VFS::the().root_custody();
auto process = adopt_ref(*new Process(first_thread, parts.take_last(), uid, gid, parent_pid, false, move(cwd), nullptr, tty));
auto process = Process::create(first_thread, parts.take_last(), uid, gid, parent_pid, false, move(cwd), nullptr, tty);
if (!first_thread)
return {};
if (!process->m_fds.try_resize(m_max_open_file_descriptors)) {
@ -175,8 +175,8 @@ RefPtr<Process> Process::create_user_process(RefPtr<Thread>& first_thread, const
RefPtr<Process> Process::create_kernel_process(RefPtr<Thread>& first_thread, String&& name, void (*entry)(void*), void* entry_data, u32 affinity)
{
auto process = adopt_ref(*new Process(first_thread, move(name), (uid_t)0, (gid_t)0, ProcessID(0), true));
if (!first_thread)
auto process = Process::create(first_thread, move(name), (uid_t)0, (gid_t)0, ProcessID(0), true);
if (!first_thread || !process)
return {};
first_thread->tss().eip = (FlatPtr)entry;
first_thread->tss().esp = FlatPtr(entry_data); // entry function argument is expected to be in tss.esp
@ -203,7 +203,18 @@ void Process::unprotect_data()
MM.set_page_writable_direct(VirtualAddress { this }, true);
}
Process::Process(RefPtr<Thread>& first_thread, const String& name, uid_t uid, gid_t gid, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> cwd, RefPtr<Custody> executable, TTY* tty, Process* fork_parent)
RefPtr<Process> Process::create(RefPtr<Thread>& first_thread, const String& name, uid_t uid, gid_t gid, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> cwd, RefPtr<Custody> executable, TTY* tty, Process* fork_parent)
{
auto process = adopt_ref_if_nonnull(new Process(name, uid, gid, ppid, is_kernel_process, move(cwd), move(executable), tty));
if (!process)
return {};
auto result = process->attach_resources(first_thread, fork_parent);
if (result.is_error())
return {};
return process;
}
Process::Process(const String& name, uid_t uid, gid_t gid, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> cwd, RefPtr<Custody> executable, TTY* tty)
: m_name(move(name))
, m_is_kernel_process(is_kernel_process)
, m_executable(move(executable))
@ -224,19 +235,28 @@ Process::Process(RefPtr<Thread>& first_thread, const String& name, uid_t uid, gi
m_sgid = gid;
dbgln_if(PROCESS_DEBUG, "Created new process {}({})", m_name, this->pid().value());
}
KResult Process::attach_resources(RefPtr<Thread>& first_thread, Process* fork_parent)
{
m_space = Space::create(*this, fork_parent ? &fork_parent->space() : nullptr);
if (!m_space)
return ENOMEM;
if (fork_parent) {
// NOTE: fork() doesn't clone all threads; the thread that called fork() becomes the only thread in the new process.
first_thread = Thread::current()->clone(*this);
if (!first_thread)
return ENOMEM;
} else {
// NOTE: This non-forked code path is only taken when the kernel creates a process "manually" (at boot.)
auto thread_or_error = Thread::try_create(*this);
VERIFY(!thread_or_error.is_error());
if (thread_or_error.is_error())
return thread_or_error.error();
first_thread = thread_or_error.release_value();
first_thread->detach();
}
return KSuccess;
}
Process::~Process()

4
Kernel/Process.h
View File

@ -499,7 +499,9 @@ private:
bool add_thread(Thread&);
bool remove_thread(Thread&);
Process(RefPtr<Thread>& first_thread, const String& name, uid_t, gid_t, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> cwd = nullptr, RefPtr<Custody> executable = nullptr, TTY* = nullptr, Process* fork_parent = nullptr);
Process(const String& name, uid_t uid, gid_t gid, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> cwd, RefPtr<Custody> executable, TTY* tty);
static RefPtr<Process> create(RefPtr<Thread>& first_thread, const String& name, uid_t, gid_t, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> cwd = nullptr, RefPtr<Custody> executable = nullptr, TTY* = nullptr, Process* fork_parent = nullptr);
KResult attach_resources(RefPtr<Thread>& first_thread, Process* fork_parent);
static ProcessID allocate_pid();
void kill_threads_except_self();

4
Kernel/Syscalls/fork.cpp
View File

@ -17,8 +17,8 @@ KResultOr<pid_t> Process::sys$fork(RegisterState& regs)
{
REQUIRE_PROMISE(proc);
RefPtr<Thread> child_first_thread;
auto child = adopt_ref(*new Process(child_first_thread, m_name, uid(), gid(), pid(), m_is_kernel_process, m_cwd, m_executable, m_tty, this));
if (!child_first_thread)
auto child = Process::create(child_first_thread, m_name, uid(), gid(), pid(), m_is_kernel_process, m_cwd, m_executable, m_tty, this);
if (!child || !child_first_thread)
return ENOMEM;
child->m_root_directory = m_root_directory;
child->m_root_directory_relative_to_global_root = m_root_directory_relative_to_global_root;