fs: fix infinite loop with async recursive mkdir on Windows

If `file` is a file then on Windows `mkdir` on `file/a` returns an
`ENOENT` error while on POSIX the equivalent returns `ENOTDIR`. On the
POSIX systems `ENOTDIR` would break out of the loop but on Windows the
`ENOENT` would strip off the `a` and attempt to make `file` as a
directory. This would return `EEXIST` but the code wasn't detecting
that the existing path was a file and attempted to make `file/a` again.

PR-URL: #27207
Fixes: #27198
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>

src/node_file.cc

@@ -1289,8 +1289,15 @@ int MKDirpSync(uv_loop_t* loop, uv_fs_t* req, const std::string& path, int mode,
         }
         default:
           uv_fs_req_cleanup(req);
+          int orig_err = err;
           err = uv_fs_stat(loop, req, next_path.c_str(), nullptr);
-          if (err == 0 && !S_ISDIR(req->statbuf.st_mode)) return UV_EEXIST;
+          if (err == 0 && !S_ISDIR(req->statbuf.st_mode)) {
+            uv_fs_req_cleanup(req);
+            if (orig_err == UV_EEXIST && continuation_data.paths.size() > 0) {
+              return UV_ENOTDIR;
+            }
+            return UV_EEXIST;
+          }
           if (err < 0) return err;
           break;
       }
@@ -1357,23 +1364,32 @@ int MKDirpAsync(uv_loop_t* loop,
           break;
         }
         default:
-          if (err == UV_EEXIST &&
-              req_wrap->continuation_data->paths.size() > 0) {
-            uv_fs_req_cleanup(req);
-            MKDirpAsync(loop, req, path.c_str(),
-                        req_wrap->continuation_data->mode, nullptr);
-          } else {
+          uv_fs_req_cleanup(req);
+          // Stash err for use in the callback.
+          req->data = reinterpret_cast<void*>(static_cast<intptr_t>(err));
+          int err = uv_fs_stat(loop, req, path.c_str(),
+                               uv_fs_callback_t{[](uv_fs_t* req) {
+            FSReqBase* req_wrap = FSReqBase::from_req(req);
+            int err = req->result;
+            if (reinterpret_cast<intptr_t>(req->data) == UV_EEXIST &&
+                  req_wrap->continuation_data->paths.size() > 0) {
+              if (err == 0 && S_ISDIR(req->statbuf.st_mode)) {
+                Environment* env = req_wrap->env();
+                uv_loop_t* loop = env->event_loop();
+                std::string path = req->path;
+                uv_fs_req_cleanup(req);
+                MKDirpAsync(loop, req, path.c_str(),
+                            req_wrap->continuation_data->mode, nullptr);
+                return;
+              }
+              err = UV_ENOTDIR;
+            }
             // verify that the path pointed to is actually a directory.
+            if (err == 0 && !S_ISDIR(req->statbuf.st_mode)) err = UV_EEXIST;
             uv_fs_req_cleanup(req);
-            int err = uv_fs_stat(loop, req, path.c_str(),
-                                 uv_fs_callback_t{[](uv_fs_t* req) {
-              FSReqBase* req_wrap = FSReqBase::from_req(req);
-              int err = req->result;
-              if (err == 0 && !S_ISDIR(req->statbuf.st_mode)) err = UV_EEXIST;
-              req_wrap->continuation_data->Done(err);
-            }});
-            if (err < 0) req_wrap->continuation_data->Done(err);
-          }
+            req_wrap->continuation_data->Done(err);
+          }});
+          if (err < 0) req_wrap->continuation_data->Done(err);
           break;
       }
       break;

test/parallel/test-fs-mkdir.js

@@ -132,7 +132,25 @@ function nextdir() {
   }
 }
 
-// mkdirp when folder does not yet exist.
+// mkdirpSync when part of the path is a file.
+{
+  const filename = path.join(tmpdir.path, nextdir(), nextdir());
+  const pathname = path.join(filename, nextdir(), nextdir());
+
+  fs.mkdirSync(path.dirname(filename));
+  fs.writeFileSync(filename, '', 'utf8');
+
+  try {
+    fs.mkdirSync(pathname, { recursive: true });
+    throw new Error('unreachable');
+  } catch (err) {
+    assert.notStrictEqual(err.message, 'unreachable');
+    assert.strictEqual(err.code, 'ENOTDIR');
+    assert.strictEqual(err.syscall, 'mkdir');
+  }
+}
+
+// `mkdirp` when folder does not yet exist.
 {
   const pathname = path.join(tmpdir.path, nextdir(), nextdir());
 
@@ -149,11 +167,25 @@ function nextdir() {
 
   fs.mkdirSync(path.dirname(pathname));
   fs.writeFileSync(pathname, '', 'utf8');
-  fs.mkdir(pathname, { recursive: true }, (err) => {
+  fs.mkdir(pathname, { recursive: true }, common.mustCall((err) => {
     assert.strictEqual(err.code, 'EEXIST');
     assert.strictEqual(err.syscall, 'mkdir');
     assert.strictEqual(fs.statSync(pathname).isDirectory(), false);
-  });
+  }));
+}
+
+// `mkdirp` when part of the path is a file.
+{
+  const filename = path.join(tmpdir.path, nextdir(), nextdir());
+  const pathname = path.join(filename, nextdir(), nextdir());
+
+  fs.mkdirSync(path.dirname(filename));
+  fs.writeFileSync(filename, '', 'utf8');
+  fs.mkdir(pathname, { recursive: true }, common.mustCall((err) => {
+    assert.strictEqual(err.code, 'ENOTDIR');
+    assert.strictEqual(err.syscall, 'mkdir');
+    assert.strictEqual(fs.existsSync(pathname), false);
+  }));
 }
 
 // mkdirpSync dirname loop

test/parallel/test-fs-promises.js

@@ -310,6 +310,22 @@ async function getHandle(dest) {
       }
     }
 
+    // `mkdirp` when part of the path is a file.
+    {
+      const file = path.join(tmpDir, nextdir(), nextdir());
+      const dir = path.join(file, nextdir(), nextdir());
+      await mkdir(path.dirname(file));
+      await writeFile(file);
+      try {
+        await mkdir(dir, { recursive: true });
+        throw new Error('unreachable');
+      } catch (err) {
+        assert.notStrictEqual(err.message, 'unreachable');
+        assert.strictEqual(err.code, 'ENOTDIR');
+        assert.strictEqual(err.syscall, 'mkdir');
+      }
+    }
+
     // mkdirp ./
     {
       const dir = path.resolve(tmpDir, `${nextdir()}/./${nextdir()}`);