src: ignore SIGXFSZ, don't terminate (ulimit -f)

Ignore SIGXFSZ signals so that exceeding RLIMIT_FSIZE makes the
offending system call fail with EFBIG instead of terminating the
process.

PR-URL: #27798
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

src/node.cc

@@ -517,7 +517,7 @@ inline void PlatformInit() {
   for (unsigned nr = 1; nr < kMaxSignal; nr += 1) {
     if (nr == SIGKILL || nr == SIGSTOP)
       continue;
-    act.sa_handler = (nr == SIGPIPE) ? SIG_IGN : SIG_DFL;
+    act.sa_handler = (nr == SIGPIPE || nr == SIGXFSZ) ? SIG_IGN : SIG_DFL;
     CHECK_EQ(0, sigaction(nr, &act, nullptr));
   }
 #endif  // !NODE_SHARED_MODE

test/parallel/test-fs-write-sigxfsz.js

@@ -0,0 +1,32 @@
+// Check that exceeding RLIMIT_FSIZE fails with EFBIG
+// rather than terminating the process with SIGXFSZ.
+'use strict';
+const common = require('../common');
+const tmpdir = require('../common/tmpdir');
+
+const assert = require('assert');
+const child_process = require('child_process');
+const fs = require('fs');
+const path = require('path');
+
+if (common.isWindows)
+  common.skip('no RLIMIT_FSIZE on Windows');
+
+if (process.config.variables.node_shared)
+  common.skip('SIGXFSZ signal handler not installed in shared library mode');
+
+if (process.argv[2] === 'child') {
+  const filename = path.join(tmpdir.path, 'efbig.txt');
+  tmpdir.refresh();
+  fs.writeFileSync(filename, '.'.repeat(1 << 16));  // Exceeds RLIMIT_FSIZE.
+} else {
+  const cmd = `ulimit -f 1 && '${process.execPath}' '${__filename}' child`;
+  const result = child_process.spawnSync('/bin/sh', ['-c', cmd]);
+  const haystack = result.stderr.toString();
+  const needle = 'Error: EFBIG: file too large, write';
+  const ok = haystack.includes(needle);
+  if (!ok) console.error(haystack);
+  assert(ok);
+  assert.strictEqual(result.status, 1);
+  assert.strictEqual(result.stdout.toString(), '');
+}