src: fix OOB reads in process.title getter

src/node_errors.cc

@@ -242,12 +242,11 @@ void AppendExceptionLine(Environment* env,
 }
 
 [[noreturn]] void Assert(const AssertionInfo& info) {
-  char name[1024];
-  GetHumanReadableProcessName(&name);
+  std::string name = GetHumanReadableProcessName();
 
   fprintf(stderr,
           "%s: %s:%s%s Assertion `%s' failed.\n",
-          name,
+          name.c_str(),
           info.file_line,
           info.function,
           *info.function ? ":" : "",

src/node_internals.h

@@ -95,8 +95,8 @@ void ResetStdio();  // Safe to call more than once and from signal handlers.
 void SignalExit(int signal, siginfo_t* info, void* ucontext);
 #endif
 
+std::string GetProcessTitle(const char* default_title);
 std::string GetHumanReadableProcessName();
-void GetHumanReadableProcessName(char (*name)[1024]);
 
 void InitializeContextRuntime(v8::Local<v8::Context>);
 

src/node_process_object.cc

@@ -32,11 +32,11 @@ using v8::Value;
 
 static void ProcessTitleGetter(Local<Name> property,
                                const PropertyCallbackInfo<Value>& info) {
-  char buffer[512];
-  uv_get_process_title(buffer, sizeof(buffer));
+  std::string title = GetProcessTitle("node");
   info.GetReturnValue().Set(
-      String::NewFromUtf8(info.GetIsolate(), buffer, NewStringType::kNormal)
-          .ToLocalChecked());
+      String::NewFromUtf8(info.GetIsolate(), title.data(),
+                          NewStringType::kNormal, title.size())
+      .ToLocalChecked());
 }
 
 static void ProcessTitleSetter(Local<Name> property,

src/node_v8_platform-inl.h

@@ -21,12 +21,12 @@ class NodeTraceStateObserver
     : public v8::TracingController::TraceStateObserver {
  public:
   inline void OnTraceEnabled() override {
-    char name_buffer[512];
-    if (uv_get_process_title(name_buffer, sizeof(name_buffer)) == 0) {
+    std::string title = GetProcessTitle("");
+    if (!title.empty()) {
       // Only emit the metadata event if the title can be retrieved
       // successfully. Ignore it otherwise.
       TRACE_EVENT_METADATA1(
-          "__metadata", "process_name", "name", TRACE_STR_COPY(name_buffer));
+          "__metadata", "process_name", "name", TRACE_STR_COPY(title.c_str()));
     }
     TRACE_EVENT_METADATA1("__metadata",
                           "version",

src/util.cc

@@ -22,6 +22,7 @@
 #include "util.h"  // NOLINT(build/include_inline)
 #include "util-inl.h"
 
+#include "debug_utils-inl.h"
 #include "env-inl.h"
 #include "node_buffer.h"
 #include "node_errors.h"
@@ -45,6 +46,7 @@
 
 #include <atomic>
 #include <cstdio>
+#include <cstring>
 #include <iomanip>
 #include <sstream>
 
@@ -133,17 +135,30 @@ void LowMemoryNotification() {
   }
 }
 
-std::string GetHumanReadableProcessName() {
-  char name[1024];
-  GetHumanReadableProcessName(&name);
-  return name;
+std::string GetProcessTitle(const char* default_title) {
+  std::string buf(16, '\0');
+
+  for (;;) {
+    const int rc = uv_get_process_title(&buf[0], buf.size());
+
+    if (rc == 0)
+      break;
+
+    if (rc != UV_ENOBUFS)
+      return default_title;
+
+    buf.resize(2 * buf.size());
+  }
+
+  // Strip excess trailing nul bytes. Using strlen() here is safe,
+  // uv_get_process_title() always zero-terminates the result.
+  buf.resize(strlen(&buf[0]));
+
+  return buf;
 }
 
-void GetHumanReadableProcessName(char (*name)[1024]) {
-  // Leave room after title for pid, which can be up to 20 digits for 64 bit.
-  char title[1000] = "Node.js";
-  uv_get_process_title(title, sizeof(title));
-  snprintf(*name, sizeof(*name), "%s[%d]", title, uv_os_getpid());
+std::string GetHumanReadableProcessName() {
+  return SPrintF("%s[%d]", GetProcessTitle("Node.js"), uv_os_getpid());
 }
 
 std::vector<std::string> SplitString(const std::string& in, char delim) {

test/parallel/test-process-title.js

@@ -0,0 +1,22 @@
+'use strict';
+const common = require('../common');
+const { spawnSync } = require('child_process');
+const { strictEqual } = require('assert');
+
+// FIXME add sunos support
+if (common.isSunOS)
+  common.skip(`Unsupported platform [${process.platform}]`);
+// FIXME add IBMi support
+if (common.isIBMi)
+  common.skip('Unsupported platform IBMi');
+
+// Explicitly assigning to process.title before starting the child process
+// is necessary otherwise *its* process.title is whatever the last
+// SetConsoleTitle() call in our process tree set it to.
+// Can be removed when https://github.com/libuv/libuv/issues/2667 is fixed.
+if (common.isWindows)
+  process.title = process.execPath;
+
+const xs = 'x'.repeat(1024);
+const proc = spawnSync(process.execPath, ['-p', 'process.title', xs]);
+strictEqual(proc.stdout.toString().trim(), process.execPath);