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Hendrik Liebau
bcb680c08c
While walking a path, `realpathSync` skips the components it already knows are real, and in that branch it reads the shared stat buffer to decide whether the walk has reached a pipe or a socket. That buffer holds the result of the last stat made anywhere in the process rather than the last one made by the walk, so an unrelated stat of a FIFO ends the walk early and the path comes back with its symlinks unresolved. The unresolved path is then written to the cache, so every later resolution repeats it. The walk only takes that branch once the ancestors are established as real, which is the state the module loader's cache is in. The test goes through `require()` to reach it, where the stale read costs a second copy of a module reached through a symlink. Signed-off-by: Hendrik Liebau <mail@hendrik-liebau.de> PR-URL: https://github.com/nodejs/node/pull/65113 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
74 lines
2.4 KiB
JavaScript
74 lines
2.4 KiB
JavaScript
// Flags: --expose-internals
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'use strict';
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// Resolving a path must not depend on what was stat'ed before it.
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//
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// While walking a path, realpath skips the components it already knows are
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// real, and in that branch it consulted the shared stat buffer to decide
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// whether the walk had reached a pipe or a socket. That buffer holds the result
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// of the last stat made anywhere in the process, so an unrelated stat of a FIFO
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// made the walk stop early and hand back the path with its symlinks unresolved.
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// The unresolved path is then cached, so every later resolution repeats it.
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const common = require('../common');
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if (common.isWindows)
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common.skip('no mkfifo on Windows');
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const assert = require('assert');
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const fs = require('fs');
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const path = require('path');
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const { execFileSync } = require('child_process');
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const { realpathCacheKey } = require('internal/fs/utils');
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const tmpdir = require('../common/tmpdir');
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tmpdir.refresh();
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const pkg = tmpdir.resolve('pkg');
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const link = tmpdir.resolve('pkg-link');
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const fifo = tmpdir.resolve('fifo');
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fs.mkdirSync(pkg);
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fs.writeFileSync(path.join(pkg, 'index.js'), 'module.exports = {};\n');
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fs.writeFileSync(tmpdir.resolve('warm.js'), 'module.exports = {};\n');
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fs.symlinkSync('pkg', link);
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execFileSync('mkfifo', [fifo]);
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const throughLink = path.join(link, 'index.js');
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const throughReal = path.join(pkg, 'index.js');
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// The walk only skips a component once something has established it as real. A
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// cache carrying the ancestors is that state, and it is the state the module
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// loader's own cache is in after it has resolved anything else under the
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// directory.
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function ancestorCache() {
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const cache = new Map();
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let dir = '';
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for (const part of tmpdir.path.split(path.sep).slice(1)) {
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dir += path.sep + part;
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cache.set(dir, dir);
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}
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return cache;
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}
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fs.statSync(path.join(pkg, 'index.js'));
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assert.strictEqual(
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fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
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throughReal,
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);
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fs.statSync(fifo);
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assert.strictEqual(
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fs.realpathSync(throughLink, { [realpathCacheKey]: ancestorCache() }),
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throughReal,
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);
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// What the stale read costs through the module loader, whose cache puts the
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// walk in that same state: the symlink stays unresolved, so the file is loaded
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// a second time under a second name.
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require(tmpdir.resolve('warm.js'));
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fs.statSync(fifo);
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assert.strictEqual(require.resolve(throughLink), throughReal);
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assert.strictEqual(require(throughLink), require(throughReal));
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