buffer: stop alloc() uninitialized memory return

CVE-2018-7166 Discovered by ChALkeR - Сковорода Никита Андреевич Prevent Buffer.alloc(size, fill, number) from returning uninitialized memory. Fixes: nodejs-private/security#202 PR-URL: nodejs-private/node-private#137 Reviewed-By: Rod Vagg <[email protected]> Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Evan Lucas <[email protected]> Reviewed-By: Сковорода Никита Андреевич <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

Author: cjihrig

lib/buffer.js

@@ -278,7 +278,8 @@ function assertSize(size){
 Buffer.alloc=functionalloc(size,fill,encoding){
 assertSize(size);
 if(fill!==undefined&&fill!==0&&size>0){
-return_fill(createUnsafeBuffer(size),fill,encoding);
+constbuf=createUnsafeBuffer(size);
+return_fill(buf,fill,0,buf.length,encoding);
 }
 returnnewFastBuffer(size);
 };

test/parallel/test-buffer-alloc.js

@@ -1039,3 +1039,10 @@ common.expectsError(() =>{
 code: 'ERR_INVALID_ARG_VALUE',
 type: TypeError
 });
+
+common.expectsError(()=>{
+Buffer.alloc(40,'x',20);
+},{
+code: 'ERR_INVALID_ARG_TYPE',
+type: TypeError
+});