fs: account for buffer alloc failure in readFile

PR-URL: #16219
Refs: #15362
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/fs.js

@@ -457,7 +457,11 @@ function readFileAfterStat(err) {
     return context.close(err);
   }
 
-  context.buffer = Buffer.allocUnsafeSlow(size);
+  try {
+    context.buffer = Buffer.allocUnsafeSlow(size);
+  } catch (err) {
+    return context.close(err);
+  }
   context.read();
 }
 
@@ -492,27 +496,21 @@ function readFileAfterClose(err) {
   if (context.err || err)
     return callback(context.err || err);
 
-  if (context.size === 0)
-    buffer = Buffer.concat(context.buffers, context.pos);
-  else if (context.pos < context.size)
-    buffer = context.buffer.slice(0, context.pos);
-  else
-    buffer = context.buffer;
-
-  if (context.encoding) {
-    return tryToString(buffer, context.encoding, callback);
-  }
-
-  callback(null, buffer);
-}
-
-function tryToString(buf, encoding, callback) {
   try {
-    buf = buf.toString(encoding);
+    if (context.size === 0)
+      buffer = Buffer.concat(context.buffers, context.pos);
+    else if (context.pos < context.size)
+      buffer = context.buffer.slice(0, context.pos);
+    else
+      buffer = context.buffer;
+
+    if (context.encoding)
+      buffer = buffer.toString(context.encoding);
   } catch (err) {
     return callback(err);
   }
-  callback(null, buf);
+
+  callback(null, buffer);
 }
 
 function tryStatSync(fd, isUserFd) {

test/sequential/test-fs-readfile-tostring-fail.js

@@ -29,7 +29,8 @@ stream.on('finish', common.mustCall(function() {
   // make sure that the toString does not throw an error
   fs.readFile(file, 'utf8', common.mustCall(function(err, buf) {
     assert.ok(err instanceof Error);
-    assert.strictEqual('"toString()" failed', err.message);
+    assert(/^(Array buffer allocation failed|"toString\(\)" failed)$/
+             .test(err.message));
     assert.strictEqual(buf, undefined);
   }));
 }));