fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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fs: fix realpath leaving symlinks unresolved after an unrelated stat #65113

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6307028
test: cover `realpathSync` resolving symlinks after a FIFO stat
unstubbable Aug 7, 2026
fc87eed
fs: stop reading the shared stat buffer in `realpathSync`
unstubbable Aug 7, 2026
95f5674
test: assert `realpathSync` directly, not only through `require()`
unstubbable Aug 8, 2026
1deb9b8
fs: stop reading the shared stat buffer in async `realpath`
unstubbable Aug 8, 2026
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25 changes: 18 additions & 7 deletions lib/fs.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
FSReqCallback,
statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
const seenLinks = new SafeMap();
const knownHard = new SafeSet();
const original = p;
// Whether the symlink this walk resolved last pointed at a pipe or a
// socket, which is where the walk stops. It cannot be read back from the
// shared stat buffer, which holds the last stat made anywhere in the
// process rather than the last one made here.
let reachedPipeOrSocket = false;

// Current character position in p
let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

// Continue if not a symlink, break if a pipe/socket
if (knownHard.has(base) || cache?.get(base) === base) {
if (isFileType(statValues, S_IFIFO) ||
isFileType(statValues, S_IFSOCK)) {
if (reachedPipeOrSocket) {
break;
}
continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
}
}
if (linkTarget === null) {
binding.stat(base, false, undefined, true);
const targetStats = binding.stat(base, false, undefined, true);
reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
isFileType(targetStats, S_IFSOCK);
linkTarget = binding.readlink(base, undefined);
}
resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

const seenLinks = new SafeMap();
const knownHard = new SafeSet();
// Whether the symlink this walk resolved last pointed at a pipe or a
// socket, which is where the walk stops. It cannot be read back from the
// shared stat buffer, which holds the last stat made anywhere in the
// process rather than the last one made here.
let reachedPipeOrSocket = false;

// Current character position in p
let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

// Continue if not a symlink, break if a pipe/socket
if (knownHard.has(base)) {
if (isFileType(statValues, S_IFIFO) ||
isFileType(statValues, S_IFSOCK)) {
if (reachedPipeOrSocket) {
return callback(null, encodeRealpathResult(p, options));
}
return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
return gotTarget(null, seenLinks.get(id));
}
}
fs.stat(base, (err) => {
fs.stat(base, (err, targetStats) => {
if (err) return callback(err);

reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

fs.readlink(base, (err, target) => {
if (!isWindows) seenLinks.set(id, target);
gotTarget(err, target);
Expand Down
62 changes: 62 additions & 0 deletions test/parallel/test-fs-realpath-async-stale-stat-values.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
if (settled) return;
fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
settled = true;
error = err;
resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
assert.ifError(error);
assert.strictEqual(resolvedPath, expected);
});
73 changes: 73 additions & 0 deletions test/parallel/test-fs-realpath-stale-stat-values.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
const cache = new Map();
let dir = '';
for (const part of tmpdir.path.split(path.sep).slice(1)) {
dir += path.sep + part;
cache.set(dir, dir);
}
return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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fs: fix realpath leaving symlinks unresolved after an unrelated stat
#65113
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6307028

test: cover `realpathSync` resolving symlinks after a FIFO stat


unstubbable Aug 7, 2026
fc87eed

fs: stop reading the shared stat buffer in `realpathSync`


unstubbable Aug 7, 2026
95f5674

test: assert `realpathSync` directly, not only through `require()`


unstubbable Aug 8, 2026
1deb9b8

fs: stop reading the shared stat buffer in async `realpath`


unstubbable Aug 8, 2026

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25 changes: 18 additions & 7 deletions
lib/fs.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
 FSReqCallback,
 statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 const original = p;
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base) || cache?.get(base) === base) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 break;
 }
 continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
 }
 }
 if (linkTarget === null) {
 binding.stat(base, false, undefined, true);
 const targetStats = binding.stat(base, false, undefined, true);
 reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
 isFileType(targetStats, S_IFSOCK);
 linkTarget = binding.readlink(base, undefined);
 }
 resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base)) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 return callback(null, encodeRealpathResult(p, options));
 }
 return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
 return gotTarget(null, seenLinks.get(id));
 }
 }
 fs.stat(base, (err) => {
 fs.stat(base, (err, targetStats) => {
 if (err) return callback(err);

 reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

 fs.readlink(base, (err, target) => {
 if (!isWindows) seenLinks.set(id, target);
 gotTarget(err, target);
Expand Down

62 changes: 62 additions & 0 deletions
test/parallel/test-fs-realpath-async-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
 if (settled) return;
 fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
 settled = true;
 error = err;
 resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
 assert.ifError(error);
 assert.strictEqual(resolvedPath, expected);
});

73 changes: 73 additions & 0 deletions
test/parallel/test-fs-realpath-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
 const cache = new Map();
 let dir = '';
 for (const part of tmpdir.path.split(path.sep).slice(1)) {
 dir += path.sep + part;
 cache.set(dir, dir);
 }
 return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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 Open

unstubbable
wants to merge
4
commits into

base:main
Choose a base branch

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+153

−7

 Open


fs: fix realpath leaving symlinks unresolved after an unrelated stat
#65113
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6307028

test: cover `realpathSync` resolving symlinks after a FIFO stat


unstubbable Aug 7, 2026
fc87eed

fs: stop reading the shared stat buffer in `realpathSync`


unstubbable Aug 7, 2026
95f5674

test: assert `realpathSync` directly, not only through `require()`


unstubbable Aug 8, 2026
1deb9b8

fs: stop reading the shared stat buffer in async `realpath`


unstubbable Aug 8, 2026

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25 changes: 18 additions & 7 deletions
lib/fs.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
 FSReqCallback,
 statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 const original = p;
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base) || cache?.get(base) === base) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 break;
 }
 continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
 }
 }
 if (linkTarget === null) {
 binding.stat(base, false, undefined, true);
 const targetStats = binding.stat(base, false, undefined, true);
 reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
 isFileType(targetStats, S_IFSOCK);
 linkTarget = binding.readlink(base, undefined);
 }
 resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base)) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 return callback(null, encodeRealpathResult(p, options));
 }
 return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
 return gotTarget(null, seenLinks.get(id));
 }
 }
 fs.stat(base, (err) => {
 fs.stat(base, (err, targetStats) => {
 if (err) return callback(err);

 reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

 fs.readlink(base, (err, target) => {
 if (!isWindows) seenLinks.set(id, target);
 gotTarget(err, target);
Expand Down

62 changes: 62 additions & 0 deletions
test/parallel/test-fs-realpath-async-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
 if (settled) return;
 fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
 settled = true;
 error = err;
 resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
 assert.ifError(error);
 assert.strictEqual(resolvedPath, expected);
});

73 changes: 73 additions & 0 deletions
test/parallel/test-fs-realpath-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
 const cache = new Map();
 let dir = '';
 for (const part of tmpdir.path.split(path.sep).slice(1)) {
 dir += path.sep + part;
 cache.set(dir, dir);
 }
 return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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fs: fix realpath leaving symlinks unresolved after an unrelated stat
#65113
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6307028

test: cover `realpathSync` resolving symlinks after a FIFO stat


unstubbable Aug 7, 2026
fc87eed

fs: stop reading the shared stat buffer in `realpathSync`


unstubbable Aug 7, 2026
95f5674

test: assert `realpathSync` directly, not only through `require()`


unstubbable Aug 8, 2026
1deb9b8

fs: stop reading the shared stat buffer in async `realpath`


unstubbable Aug 8, 2026

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25 changes: 18 additions & 7 deletions
lib/fs.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
 FSReqCallback,
 statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 const original = p;
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base) || cache?.get(base) === base) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 break;
 }
 continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
 }
 }
 if (linkTarget === null) {
 binding.stat(base, false, undefined, true);
 const targetStats = binding.stat(base, false, undefined, true);
 reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
 isFileType(targetStats, S_IFSOCK);
 linkTarget = binding.readlink(base, undefined);
 }
 resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base)) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 return callback(null, encodeRealpathResult(p, options));
 }
 return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
 return gotTarget(null, seenLinks.get(id));
 }
 }
 fs.stat(base, (err) => {
 fs.stat(base, (err, targetStats) => {
 if (err) return callback(err);

 reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

 fs.readlink(base, (err, target) => {
 if (!isWindows) seenLinks.set(id, target);
 gotTarget(err, target);
Expand Down

62 changes: 62 additions & 0 deletions
test/parallel/test-fs-realpath-async-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
 if (settled) return;
 fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
 settled = true;
 error = err;
 resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
 assert.ifError(error);
 assert.strictEqual(resolvedPath, expected);
});

73 changes: 73 additions & 0 deletions
test/parallel/test-fs-realpath-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
 const cache = new Map();
 let dir = '';
 for (const part of tmpdir.path.split(path.sep).slice(1)) {
 dir += path.sep + part;
 cache.set(dir, dir);
 }
 return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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 Open

unstubbable
wants to merge
4
commits into

base:main
Choose a base branch

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+153

−7

 Open


fs: fix realpath leaving symlinks unresolved after an unrelated stat
#65113
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6307028

test: cover `realpathSync` resolving symlinks after a FIFO stat


unstubbable Aug 7, 2026
fc87eed

fs: stop reading the shared stat buffer in `realpathSync`


unstubbable Aug 7, 2026
95f5674

test: assert `realpathSync` directly, not only through `require()`


unstubbable Aug 8, 2026
1deb9b8

fs: stop reading the shared stat buffer in async `realpath`


unstubbable Aug 8, 2026

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25 changes: 18 additions & 7 deletions
lib/fs.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
 FSReqCallback,
 statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 const original = p;
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base) || cache?.get(base) === base) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 break;
 }
 continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
 }
 }
 if (linkTarget === null) {
 binding.stat(base, false, undefined, true);
 const targetStats = binding.stat(base, false, undefined, true);
 reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
 isFileType(targetStats, S_IFSOCK);
 linkTarget = binding.readlink(base, undefined);
 }
 resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base)) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 return callback(null, encodeRealpathResult(p, options));
 }
 return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
 return gotTarget(null, seenLinks.get(id));
 }
 }
 fs.stat(base, (err) => {
 fs.stat(base, (err, targetStats) => {
 if (err) return callback(err);

 reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

 fs.readlink(base, (err, target) => {
 if (!isWindows) seenLinks.set(id, target);
 gotTarget(err, target);
Expand Down

62 changes: 62 additions & 0 deletions
test/parallel/test-fs-realpath-async-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
 if (settled) return;
 fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
 settled = true;
 error = err;
 resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
 assert.ifError(error);
 assert.strictEqual(resolvedPath, expected);
});

73 changes: 73 additions & 0 deletions
test/parallel/test-fs-realpath-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
 const cache = new Map();
 let dir = '';
 for (const part of tmpdir.path.split(path.sep).slice(1)) {
 dir += path.sep + part;
 cache.set(dir, dir);
 }
 return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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fs: fix realpath leaving symlinks unresolved after an unrelated stat
#65113
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6307028

test: cover `realpathSync` resolving symlinks after a FIFO stat


unstubbable Aug 7, 2026
fc87eed

fs: stop reading the shared stat buffer in `realpathSync`


unstubbable Aug 7, 2026
95f5674

test: assert `realpathSync` directly, not only through `require()`


unstubbable Aug 8, 2026
1deb9b8

fs: stop reading the shared stat buffer in async `realpath`


unstubbable Aug 8, 2026

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25 changes: 18 additions & 7 deletions
lib/fs.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
 FSReqCallback,
 statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 const original = p;
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base) || cache?.get(base) === base) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 break;
 }
 continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
 }
 }
 if (linkTarget === null) {
 binding.stat(base, false, undefined, true);
 const targetStats = binding.stat(base, false, undefined, true);
 reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
 isFileType(targetStats, S_IFSOCK);
 linkTarget = binding.readlink(base, undefined);
 }
 resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base)) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 return callback(null, encodeRealpathResult(p, options));
 }
 return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
 return gotTarget(null, seenLinks.get(id));
 }
 }
 fs.stat(base, (err) => {
 fs.stat(base, (err, targetStats) => {
 if (err) return callback(err);

 reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

 fs.readlink(base, (err, target) => {
 if (!isWindows) seenLinks.set(id, target);
 gotTarget(err, target);
Expand Down

62 changes: 62 additions & 0 deletions
test/parallel/test-fs-realpath-async-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
 if (settled) return;
 fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
 settled = true;
 error = err;
 resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
 assert.ifError(error);
 assert.strictEqual(resolvedPath, expected);
});

73 changes: 73 additions & 0 deletions
test/parallel/test-fs-realpath-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
 const cache = new Map();
 let dir = '';
 for (const part of tmpdir.path.split(path.sep).slice(1)) {
 dir += path.sep + part;
 cache.set(dir, dir);
 }
 return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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fs: fix realpath leaving symlinks unresolved after an unrelated stat
#65113
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6307028

test: cover `realpathSync` resolving symlinks after a FIFO stat


unstubbable Aug 7, 2026
fc87eed

fs: stop reading the shared stat buffer in `realpathSync`


unstubbable Aug 7, 2026
95f5674

test: assert `realpathSync` directly, not only through `require()`


unstubbable Aug 8, 2026
1deb9b8

fs: stop reading the shared stat buffer in async `realpath`


unstubbable Aug 8, 2026

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25 changes: 18 additions & 7 deletions
lib/fs.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
 FSReqCallback,
 statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 const original = p;
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base) || cache?.get(base) === base) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 break;
 }
 continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
 }
 }
 if (linkTarget === null) {
 binding.stat(base, false, undefined, true);
 const targetStats = binding.stat(base, false, undefined, true);
 reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
 isFileType(targetStats, S_IFSOCK);
 linkTarget = binding.readlink(base, undefined);
 }
 resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base)) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 return callback(null, encodeRealpathResult(p, options));
 }
 return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
 return gotTarget(null, seenLinks.get(id));
 }
 }
 fs.stat(base, (err) => {
 fs.stat(base, (err, targetStats) => {
 if (err) return callback(err);

 reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

 fs.readlink(base, (err, target) => {
 if (!isWindows) seenLinks.set(id, target);
 gotTarget(err, target);
Expand Down

62 changes: 62 additions & 0 deletions
test/parallel/test-fs-realpath-async-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
 if (settled) return;
 fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
 settled = true;
 error = err;
 resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
 assert.ifError(error);
 assert.strictEqual(resolvedPath, expected);
});

73 changes: 73 additions & 0 deletions
test/parallel/test-fs-realpath-stale-stat-values.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
 const cache = new Map();
 let dir = '';
 for (const part of tmpdir.path.split(path.sep).slice(1)) {
 dir += path.sep + part;
 cache.set(dir, dir);
 }
 return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
fs: fix realpath leaving symlinks unresolved after an unrelated stat#65113

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unstubbable
wants to merge
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commits into

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Choose a base branch

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+153

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fs: fix realpath leaving symlinks unresolved after an unrelated stat
#65113
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6307028

test: cover `realpathSync` resolving symlinks after a FIFO stat


unstubbable Aug 7, 2026
fc87eed

fs: stop reading the shared stat buffer in `realpathSync`


unstubbable Aug 7, 2026
95f5674

test: assert `realpathSync` directly, not only through `require()`


unstubbable Aug 8, 2026
1deb9b8

fs: stop reading the shared stat buffer in async `realpath`


unstubbable Aug 8, 2026

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25 changes: 18 additions & 7 deletions
lib/fs.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -81,7 +81,6 @@ const {

const {
 FSReqCallback,
 statValues,
} = binding;
const { toPathIfFileURL } = require('internal/url');
const {
Expand DownExpand Up@@ -3254,6 +3253,11 @@ function realpathSync(p, options) {
 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 const original = p;
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3297,8 +3301,7 @@ function realpathSync(p, options) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base) || cache?.get(base) === base) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 break;
 }
 continue;
Expand DownExpand Up@@ -3336,7 +3339,9 @@ function realpathSync(p, options) {
 }
 }
 if (linkTarget === null) {
 binding.stat(base, false, undefined, true);
 const targetStats = binding.stat(base, false, undefined, true);
 reachedPipeOrSocket = isFileType(targetStats, S_IFIFO) ||
 isFileType(targetStats, S_IFSOCK);
 linkTarget = binding.readlink(base, undefined);
 }
 resolvedLink = pathModule.resolve(previous, linkTarget);
Expand DownExpand Up@@ -3418,6 +3423,11 @@ function realpath(p, options, callback) {

 const seenLinks = new SafeMap();
 const knownHard = new SafeSet();
 // Whether the symlink this walk resolved last pointed at a pipe or a
 // socket, which is where the walk stops. It cannot be read back from the
 // shared stat buffer, which holds the last stat made anywhere in the
 // process rather than the last one made here.
 let reachedPipeOrSocket = false;

 // Current character position in p
 let pos;
Expand DownExpand Up@@ -3466,8 +3476,7 @@ function realpath(p, options, callback) {

 // Continue if not a symlink, break if a pipe/socket
 if (knownHard.has(base)) {
 if (isFileType(statValues, S_IFIFO) ||
 isFileType(statValues, S_IFSOCK)) {
 if (reachedPipeOrSocket) {
 return callback(null, encodeRealpathResult(p, options));
 }
 return process.nextTick(LOOP);
Expand DownExpand Up@@ -3497,9 +3506,11 @@ function realpath(p, options, callback) {
 return gotTarget(null, seenLinks.get(id));
 }
 }
 fs.stat(base, (err) => {
 fs.stat(base, (err, targetStats) => {
 if (err) return callback(err);

 reachedPipeOrSocket = targetStats.isFIFO() || targetStats.isSocket();

 fs.readlink(base, (err, target) => {
 if (!isWindows) seenLinks.set(id, target);
 gotTarget(err, target);
Expand Down

62 changes: 62 additions & 0 deletions
test/parallel/test-fs-realpath-async-stale-stat-values.js

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@@ -0,0 +1,62 @@
'use strict';

// The async realpath() reads the shared stat buffer the same way realpathSync()
// did, to decide whether the walk has reached a pipe or a socket. The walk's
// own fs.stat() does leave the right value there, but it is not read until
// after fs.readlink() and a process.nextTick(), and any stat completing in that
// window replaces it.
//
// Truncating the walk only costs something when a second symlink follows the
// one being resolved, so the path used here has two.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const real = tmpdir.resolve('real');
const pkg = tmpdir.resolve('pkg');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(real);
fs.mkdirSync(pkg);
fs.writeFileSync(path.join(real, 'index.js'), '');
fs.symlinkSync(path.join('..', 'real'), path.join(pkg, 'sub'));
fs.symlinkSync('pkg', tmpdir.resolve('link'));
execFileSync('mkfifo', [fifo]);

const throughLinks = tmpdir.resolve('link', 'sub', 'index.js');
const expected = path.join(real, 'index.js');

// Keep stats of the FIFO completing for as long as the walk runs, so that one
// of them lands in the buffer during the window.
let settled = false;
(function statFifo() {
 if (settled) return;
 fs.stat(fifo, statFifo);
})();

let error;
let resolvedPath;

fs.realpath(throughLinks, common.mustCall((err, resolved) => {
 settled = true;
 error = err;
 resolvedPath = resolved;
}));

// Asserted on exit rather than in the callback. An assertion that fails inside
// this callback is lost: it does not reach an `uncaughtException` handler and
// the process still exits 0, so the test would pass over the bug it covers.
process.on('exit', () => {
 assert.ifError(error);
 assert.strictEqual(resolvedPath, expected);
});

73 changes: 73 additions & 0 deletions
test/parallel/test-fs-realpath-stale-stat-values.js

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// Flags: --expose-internals
'use strict';

// Resolving a path must not depend on what was stat'ed before it.
//
// While walking a path, realpath skips the components it already knows are
// real, and in that branch it consulted the shared stat buffer to decide
// whether the walk had reached a pipe or a socket. That buffer holds the result
// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
// made the walk stop early and hand back the path with its symlinks unresolved.
// The unresolved path is then cached, so every later resolution repeats it.

const common = require('../common');

if (common.isWindows)
 common.skip('no mkfifo on Windows');

const assert = require('assert');
const fs = require('fs');
const path = require('path');
const { execFileSync } = require('child_process');
const { realpathCacheKey } = require('internal/fs/utils');
const tmpdir = require('../common/tmpdir');

tmpdir.refresh();

const pkg = tmpdir.resolve('pkg');
const link = tmpdir.resolve('pkg-link');
const fifo = tmpdir.resolve('fifo');

fs.mkdirSync(pkg);
fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
fs.symlinkSync('pkg', link);
execFileSync('mkfifo', [fifo]);

const throughLink = path.join(link, 'index.js');
const throughReal = path.join(pkg, 'index.js');

// The walk only skips a component once something has established it as real. A
// cache carrying the ancestors is that state, and it is the state the module
// loader's own cache is in after it has resolved anything else under the
// directory.
function ancestorCache() {
 const cache = new Map();
 let dir = '';
 for (const part of tmpdir.path.split(path.sep).slice(1)) {
 dir += path.sep + part;
 cache.set(dir, dir);
 }
 return cache;
}

fs.statSync(path.join(pkg, 'index.js'));
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

fs.statSync(fifo);
assert.strictEqual(
 fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
 throughReal,
);

// What the stale read costs through the module loader, whose cache puts the
// walk in that same state: the symlink stays unresolved, so the file is loaded
// a second time under a second name.
require(tmpdir.resolve('warm.js'));
fs.statSync(fifo);

assert.strictEqual(require.resolve(throughLink), throughReal);
assert.strictEqual(require(throughLink), require(throughReal));
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