doc,test: add known path resolution issue in permission model

doc/api/permissions.md

@@ -560,6 +560,8 @@ Wildcards are supported too:
 
 There are constraints you need to know before using this system:
 
+* When the permission model is enabled, Node.js may resolve some paths
+  differently than when it is disabled.
 * Native modules are restricted by default when using the Permission Model.
 * OpenSSL engines currently cannot be requested at runtime when the Permission
   Model is enabled, affecting the built-in crypto, https, and tls modules.

test/known_issues/test-permission-model-path-resolution.js

@@ -0,0 +1,46 @@
+'use strict';
+
+// The permission model resolves paths to avoid path traversals, but in doing so
+// it potentially interprets paths differently than the operating system would.
+// This test demonstrates that merely enabling the permission model causes the
+// application to potentially access a different file than it would without the
+// permission model.
+
+const common = require('../common');
+
+const assert = require('assert');
+const { execFileSync } = require('child_process');
+const { mkdirSync, symlinkSync, writeFileSync } = require('fs');
+const path = require('path');
+
+if (common.isWindows)
+  assert.fail('not applicable to Windows');
+
+const tmpdir = require('../common/tmpdir');
+tmpdir.refresh();
+
+const a = path.join(tmpdir.path, 'a');
+const b = path.join(tmpdir.path, 'b');
+const c = path.join(tmpdir.path, 'c');
+const d = path.join(tmpdir.path, 'c/d');
+
+writeFileSync(a, 'bad');
+symlinkSync('c/d', b);
+mkdirSync(c);
+mkdirSync(d);
+writeFileSync(path.join(c, 'a'), 'good');
+
+function run(...args) {
+  const interestingPath = `${tmpdir.path}/b/../a`;
+  args = [...args, '-p', `fs.readFileSync(${JSON.stringify(interestingPath)}, 'utf8')`];
+  return execFileSync(process.execPath, args, { encoding: 'utf8' }).trim();
+}
+
+// Because this is a known_issues test, we cannot assert any assumptions besides
+// the known issue itself. Instead, do a sanity check and report success if the
+// sanity check fails.
+if (run() !== 'good') {
+  process.exit(0);
+}
+
+assert.strictEqual(run('--experimental-permission', `--allow-fs-read=${tmpdir.path}`), 'good');