From 967a6a2021d64fec9074e5131cf8b2bb3b07562e Mon Sep 17 00:00:00 2001
From: Jarred Sumner <jarred@jarredsumner.com>
Date: Tue, 13 Jan 2026 23:05:46 -0800
Subject: [PATCH] Fix blocking realpathSync call (#26056)

### What does this PR do?

### How did you verify your code works?

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
---
 src/bun.js/bindings/c-bindings.cpp |  2 +-
 src/bun.js/node/node_fs.zig        |  4 +++-
 test/js/node/fs/fs.test.ts         | 21 ++++++++++++++++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/bun.js/bindings/c-bindings.cpp b/src/bun.js/bindings/c-bindings.cpp
index cfd507e78f..71c3e46c79 100644
--- a/src/bun.js/bindings/c-bindings.cpp
+++ b/src/bun.js/bindings/c-bindings.cpp
@@ -73,7 +73,7 @@ extern "C" bool is_executable_file(const char* path)
 {
 #if defined(O_EXEC)
     // O_EXEC is macOS specific
-    int fd = open(path, O_EXEC | O_CLOEXEC, 0);
+    int fd = open(path, O_EXEC | O_CLOEXEC | O_NONBLOCK | O_NOCTTY, 0);
     if (fd < 0)
         return false;
     close(fd);
diff --git a/src/bun.js/node/node_fs.zig b/src/bun.js/node/node_fs.zig
index 0baa7b8a94..d8b27f6cf6 100644
--- a/src/bun.js/node/node_fs.zig
+++ b/src/bun.js/node/node_fs.zig
@@ -5499,7 +5499,9 @@ pub const NodeFS = struct {
             // O_PATH is faster
             bun.O.PATH
         else
-            bun.O.RDONLY;
+            // O_NONBLOCK prevents blocking on a FIFO.
+            // O_NOCTTY prevents acquiring a controlling terminal.
+            bun.O.RDONLY | bun.O.NONBLOCK | bun.O.NOCTTY;
 
         const fd = switch (bun.sys.open(path, flags, 0)) {
             .err => |err| return .{ .err = err.withPath(path) },
diff --git a/test/js/node/fs/fs.test.ts b/test/js/node/fs/fs.test.ts
index f4196f282f..d85c6a2aa7 100644
--- a/test/js/node/fs/fs.test.ts
+++ b/test/js/node/fs/fs.test.ts
@@ -1,5 +1,16 @@
 import { describe, expect, it, spyOn } from "bun:test";
-import { bunEnv, bunExe, gc, getMaxFD, isBroken, isIntelMacOS, isWindows, tempDirWithFiles, tmpdirSync } from "harness";
+import {
+  bunEnv,
+  bunExe,
+  gc,
+  getMaxFD,
+  isBroken,
+  isIntelMacOS,
+  isPosix,
+  isWindows,
+  tempDirWithFiles,
+  tmpdirSync,
+} from "harness";
 import { isAscii } from "node:buffer";
 import fs, {
   closeSync,
@@ -51,6 +62,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 
 import { spawnSync } from "bun";
+import { mkfifo } from "mkfifo";
 import { ReadStream as ReadStream_, WriteStream as WriteStream_ } from "./export-from.js";
 import { ReadStream as ReadStreamStar_, WriteStream as WriteStreamStar_ } from "./export-star-from.js";
 
@@ -1540,6 +1552,13 @@ it("symlink", () => {
   expect(realpathSync(actual)).toBe(realpathSync(import.meta.path));
 });
 
+it.if(isPosix)("realpathSync doesn't block on FIFO", () => {
+  const path = join(tmpdirSync(), "test-fs-fifo-block.fifo");
+  mkfifo(path, 0o666);
+  realpathSync(path);
+  unlinkSync(path);
+});
+
 it("readlink", () => {
   const actual = join(tmpdirSync(), "fs-readlink.txt");
   try {