From 615d3863908844400330964924ac2cad4a467736 Mon Sep 17 00:00:00 2001 From: Anna Henningsen Date: Tue, 23 Apr 2019 21:08:14 +0200 Subject: [PATCH] child_process: only stop readable side of stream passed to proc Closing the underlying resource completely has the unwanted side effect that the stream can no longer be used at all, including passing it to other child processes. What we want to avoid is accidentally reading from the stream; accordingly, it should be sufficient to stop its readable side manually, and otherwise leave the underlying resource intact. Fixes: https://github.com/nodejs/node/issues/27097 Refs: https://github.com/nodejs/node/pull/21209 PR-URL: https://github.com/nodejs/node/pull/27373 Reviewed-By: Matteo Collina Reviewed-By: Gireesh Punathil --- lib/internal/child_process.js | 23 ++++++++++---- .../test-child-process-pipe-dataflow.js | 4 +++ .../test-child-process-server-close.js | 6 ++-- ...ld-process-stdio-merge-stdouts-into-cat.js | 30 +++++++++++++++++++ ...hild-process-stdio-reuse-readable-stdio.js | 27 +++++++++++++++++ 5 files changed, 81 insertions(+), 9 deletions(-) create mode 100644 test/parallel/test-child-process-stdio-merge-stdouts-into-cat.js create mode 100644 test/parallel/test-child-process-stdio-reuse-readable-stdio.js diff --git a/lib/internal/child_process.js b/lib/internal/child_process.js index 8e6a303a2e27a5..03c0ed9159f64a 100644 --- a/lib/internal/child_process.js +++ b/lib/internal/child_process.js @@ -63,6 +63,7 @@ let freeParser; let HTTPParser; const MAX_HANDLE_RETRANSMISSIONS = 3; +const kIsUsedAsStdio = Symbol('kIsUsedAsStdio'); // This object contain function to convert TCP objects to native handle objects // and back again. @@ -278,8 +279,14 @@ function flushStdio(subprocess) { for (var i = 0; i < stdio.length; i++) { const stream = stdio[i]; - if (!stream || !stream.readable || stream._readableState.readableListening) + // TODO(addaleax): This doesn't necessarily account for all the ways in + // which data can be read from a stream, e.g. being consumed on the + // native layer directly as a StreamBase. + if (!stream || !stream.readable || + stream._readableState.readableListening || + stream[kIsUsedAsStdio]) { continue; + } stream.resume(); } } @@ -384,12 +391,16 @@ ChildProcess.prototype.spawn = function(options) { continue; } - // The stream is already cloned and piped, thus close it. + // The stream is already cloned and piped, thus stop its readable side, + // otherwise we might attempt to read from the stream when at the same time + // the child process does. if (stream.type === 'wrap') { - stream.handle.close(); - if (stream._stdio && stream._stdio instanceof EventEmitter) { - stream._stdio.emit('close'); - } + stream.handle.reading = false; + stream.handle.readStop(); + stream._stdio.pause(); + stream._stdio.readableFlowing = false; + stream._stdio._readableState.reading = false; + stream._stdio[kIsUsedAsStdio] = true; continue; } diff --git a/test/parallel/test-child-process-pipe-dataflow.js b/test/parallel/test-child-process-pipe-dataflow.js index f5068b5d366468..88a31f4ff8429b 100644 --- a/test/parallel/test-child-process-pipe-dataflow.js +++ b/test/parallel/test-child-process-pipe-dataflow.js @@ -33,6 +33,10 @@ const MB = KB * KB; grep = spawn('grep', ['x'], { stdio: [cat.stdout, 'pipe', 'pipe'] }); wc = spawn('wc', ['-c'], { stdio: [grep.stdout, 'pipe', 'pipe'] }); + // Extra checks: We never try to start reading data ourselves. + cat.stdout._handle.readStart = common.mustNotCall(); + grep.stdout._handle.readStart = common.mustNotCall(); + [cat, grep, wc].forEach((child, index) => { child.stderr.on('data', (d) => { // Don't want to assert here, as we might miss error code info. diff --git a/test/parallel/test-child-process-server-close.js b/test/parallel/test-child-process-server-close.js index ec95fed67b4fa7..d70926f2e8278e 100644 --- a/test/parallel/test-child-process-server-close.js +++ b/test/parallel/test-child-process-server-close.js @@ -8,11 +8,11 @@ const tmpdir = require('../common/tmpdir'); tmpdir.refresh(); const server = net.createServer((conn) => { - conn.on('close', common.mustCall()); - spawn(process.execPath, ['-v'], { stdio: ['ignore', conn, 'ignore'] - }).on('close', common.mustCall()); + }).on('close', common.mustCall(() => { + conn.end(); + })); }).listen(common.PIPE, () => { const client = net.connect(common.PIPE, common.mustCall()); client.on('data', () => { diff --git a/test/parallel/test-child-process-stdio-merge-stdouts-into-cat.js b/test/parallel/test-child-process-stdio-merge-stdouts-into-cat.js new file mode 100644 index 00000000000000..64373e9e160937 --- /dev/null +++ b/test/parallel/test-child-process-stdio-merge-stdouts-into-cat.js @@ -0,0 +1,30 @@ +'use strict'; +const common = require('../common'); +const assert = require('assert'); +const { spawn } = require('child_process'); + +// Regression test for https://github.com/nodejs/node/issues/27097. +// Check that (cat [p1] ; cat [p2]) | cat [p3] works. + +const p3 = spawn('cat', { stdio: ['pipe', 'pipe', 'inherit'] }); +const p1 = spawn('cat', { stdio: ['pipe', p3.stdin, 'inherit'] }); +const p2 = spawn('cat', { stdio: ['pipe', p3.stdin, 'inherit'] }); +p3.stdout.setEncoding('utf8'); + +// Write three different chunks: +// - 'hello' from this process to p1 to p3 back to us +// - 'world' from this process to p2 to p3 back to us +// - 'foobar' from this process to p3 back to us +// Do so sequentially in order to avoid race conditions. +p1.stdin.end('hello\n'); +p3.stdout.once('data', common.mustCall((chunk) => { + assert.strictEqual(chunk, 'hello\n'); + p2.stdin.end('world\n'); + p3.stdout.once('data', common.mustCall((chunk) => { + assert.strictEqual(chunk, 'world\n'); + p3.stdin.end('foobar\n'); + p3.stdout.once('data', common.mustCall((chunk) => { + assert.strictEqual(chunk, 'foobar\n'); + })); + })); +})); diff --git a/test/parallel/test-child-process-stdio-reuse-readable-stdio.js b/test/parallel/test-child-process-stdio-reuse-readable-stdio.js new file mode 100644 index 00000000000000..263270f8e8891f --- /dev/null +++ b/test/parallel/test-child-process-stdio-reuse-readable-stdio.js @@ -0,0 +1,27 @@ +'use strict'; +const common = require('../common'); +const assert = require('assert'); +const { spawn } = require('child_process'); + +// Check that, once a child process has ended, it’s safe to read from a pipe +// that the child had used as input. +// We simulate that using cat | (head -n1; ...) + +const p1 = spawn('cat', { stdio: ['pipe', 'pipe', 'inherit'] }); +const p2 = spawn('head', ['-n1'], { stdio: [p1.stdout, 'pipe', 'inherit'] }); + +// First, write the line that gets passed through p2, making 'head' exit. +p1.stdin.write('hello\n'); +p2.stdout.setEncoding('utf8'); +p2.stdout.on('data', common.mustCall((chunk) => { + assert.strictEqual(chunk, 'hello\n'); +})); +p2.on('exit', common.mustCall(() => { + // We can now use cat’s output, because 'head' is no longer reading from it. + p1.stdin.end('world\n'); + p1.stdout.setEncoding('utf8'); + p1.stdout.on('data', common.mustCall((chunk) => { + assert.strictEqual(chunk, 'world\n'); + })); + p1.stdout.resume(); +}));