Node: Infinite event loop after calling fs.realpath on 16-inch Macbook

[MMhunter]

• Version:
  10, 12 and Latest
• Platform:
  MacOS 10.15.5 (16-inch, 2019)

What steps will reproduce the bug?

just call fs.realpath with /usr/bin/tclsh as first parameter.

require('fs').realpath('/usr/bin/tclsh', console.log)

Callback will not be executed, and the node process will be in an infinite event loop. (Not dead, but having high cpu usage).

How often does it reproduce? Is there a required condition?

Every time.

What is the expected behavior?

Callback should be executed as expected.

Additional information

Little inspecting into this issue:

The link path for /usr/bin/tclsh:
/usr/bin/tclsh -> usr/bin/tclsh8.5 -> /System/Library/Frameworks/Tcl.framework/Versions/8.5/tclsh8.5

In the fs.js, the realpath function attempts to use seenLinks to store symbolicLinks that have been already visited.

However, on MacOS 10.15.5, 16-inch MacOS, calling node's fs.lstat on /usr/bin/tclsh and usr/bin/tclsh8.5 share the same dev and ino number. This means that the seenLinks for id of usr/bin/tclsh8.5 will target to itself, then the infinite loop happens.

Another interesting thing, it looks like the fs.lstat won't get the same number with terminal command stat on this system. (But they are the same on older MacBook)

Btw, fs.realpath.native works well.

[bnoordhuis]

Oh dear, that looks like another instance of node using doubles to represent inode numbers, and losing precision in the process. It should be easy to fix by switching over to bigints:

diff --git a/lib/fs.js b/lib/fs.js
index 8d2a1e044e..5319b2d375 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -1608,7 +1608,7 @@ function realpathSync(p, options) {
   // On windows, check that the root exists. On unix there is no need.
   if (isWindows && !knownHard[base]) {
     const ctx = { path: base };
-    binding.lstat(pathModule.toNamespacedPath(base), false, undefined, ctx);
+    binding.lstat(pathModule.toNamespacedPath(base), true, undefined, ctx);
     handleErrorFromBinding(ctx);
     knownHard[base] = true;
   }
@@ -1650,7 +1650,7 @@ function realpathSync(p, options) {

       const baseLong = pathModule.toNamespacedPath(base);
       const ctx = { path: base };
-      const stats = binding.lstat(baseLong, false, undefined, ctx);
+      const stats = binding.lstat(baseLong, true, undefined, ctx);
       handleErrorFromBinding(ctx);

       if (!isFileType(stats, S_IFLNK)) {
@@ -1673,7 +1673,7 @@ function realpathSync(p, options) {
       }
       if (linkTarget === null) {
         const ctx = { path: base };
-        binding.stat(baseLong, false, undefined, ctx);
+        binding.stat(baseLong, true, undefined, ctx);
         handleErrorFromBinding(ctx);
         linkTarget = binding.readlink(baseLong, undefined, undefined, ctx);
         handleErrorFromBinding(ctx);
@@ -1694,7 +1694,7 @@ function realpathSync(p, options) {
     // On windows, check that the root exists. On unix there is no need.
     if (isWindows && !knownHard[base]) {
       const ctx = { path: base };
-      binding.lstat(pathModule.toNamespacedPath(base), false, undefined, ctx);
+      binding.lstat(pathModule.toNamespacedPath(base), true, undefined, ctx);
       handleErrorFromBinding(ctx);
       knownHard[base] = true;
     }

(note: that's for fs.realpathSync(). fs.realpath() needs updating too.)

That inode number, 1152921500312396900, is well beyond the range of numbers that a 64 bits floating point number can accurately represent (which ends at 2**53.)

Am I right that stat -x /usr/bin/tclsh and stat -x /usr/bin/tclsh8.5 print different inos?