Kernel: Make Process::start_tracing_from API OOM safe

Modify the API so it's possible to propagate error on OOM failure. NonnullOwnPtr<T> is not appropriate for the ThreadTracer::create() API, so switch to OwnPtr<T>, use adopt_own_if_nonnull() to handle creation.
AmusedNetwork · May 13, 2021 · 956314f · 956314f
1 parent dba261f
commit 956314f
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Showing 4 changed files with 12 additions and 6 deletions.
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
@@ -660,9 +660,13 @@ void Process::set_tty(TTY* tty)
  m_tty = tty;
 }
 
-void Process::start_tracing_from(ProcessID tracer)
+KResult Process::start_tracing_from(ProcessID tracer)
 {
- m_tracer = ThreadTracer::create(tracer);
+ auto thread_tracer = ThreadTracer::create(tracer);
+ if (!thread_tracer)
+ return ENOMEM;
+ m_tracer = move(thread_tracer);
+ return KSuccess;
 }
 
 void Process::stop_tracing()

diff --git a/Kernel/Process.h b/Kernel/Process.h
@@ -241,7 +241,7 @@ class Process
 
  ThreadTracer* tracer() { return m_tracer.ptr(); }
  bool is_traced() const { return !!m_tracer; }
- void start_tracing_from(ProcessID tracer);
+ KResult start_tracing_from(ProcessID tracer);
  void stop_tracing();
  void tracer_trap(Thread&, const RegisterState&);
 

diff --git a/Kernel/Syscalls/ptrace.cpp b/Kernel/Syscalls/ptrace.cpp
@@ -51,7 +51,9 @@ static KResultOr<u32> handle_ptrace(const Kernel::Syscall::SC_ptrace_params& par
  if (peer_process.tracer()) {
  return EBUSY;
  }
- peer_process.start_tracing_from(caller.pid());
+ auto result = peer_process.start_tracing_from(caller.pid());
+ if (result.is_error())
+ return result.error();
  ScopedSpinLock lock(peer->get_lock());
  if (peer->state() != Thread::State::Stopped) {
  peer->send_signal(SIGSTOP, &caller);

diff --git a/Kernel/ThreadTracer.h b/Kernel/ThreadTracer.h
@@ -6,16 +6,16 @@
 
 #pragma once
 
-#include <AK/NonnullOwnPtr.h>
 #include <AK/Optional.h>
+#include <AK/OwnPtr.h>
 #include <Kernel/UnixTypes.h>
 #include <LibC/sys/arch/i386/regs.h>
 
 namespace Kernel {
 
 class ThreadTracer {
 public:
- static NonnullOwnPtr<ThreadTracer> create(ProcessID tracer) { return make<ThreadTracer>(tracer); }
+ static OwnPtr<ThreadTracer> create(ProcessID tracer) { return adopt_own_if_nonnull(new ThreadTracer(tracer)); }
 
  ProcessID tracer_pid() const { return m_tracer_pid; }
  bool has_pending_signal(u32 signal) const { return m_pending_signals & (1 << (signal - 1)); }