From c71624d1dadf3befa38a6c118b494866c3cd32cb Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Sat, 26 Oct 2019 17:37:47 -0400
Subject: [PATCH] Fix access to detached buffer when using WASM in bidi-trie

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/764

WebAssembly.Memory.grow() preserves the buffer content when
we grow it, no need to manually copy it. Doing so was
causing an access to a no longer valid ArrayBuffer.
---
 src/js/strie.js | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/js/strie.js b/src/js/strie.js
index 599cfd390..9a0a8a668 100644
--- a/src/js/strie.js
+++ b/src/js/strie.js
@@ -759,6 +759,14 @@ const roundToPageSize = v => (v + PAGE_SIZE-1) & ~(PAGE_SIZE-1);
             let newBuf;
             if ( this.wasmMemory === null ) {
                 newBuf = new Uint8Array(bufLen);
+                newBuf.set(this.buf8.subarray(0, this.buf32[TRIE1_SLOT]), 0);
+                newBuf.set(
+                    this.buf8.subarray(
+                        this.buf32[CHAR0_SLOT],
+                        this.buf32[CHAR1_SLOT]
+                    ),
+                    char0
+                );
             } else {
                 const oldPageCount = this.buf8.length >>> 16;
                 const newPageCount = (bufLen + 0xFFFF) >>> 16;
@@ -767,14 +775,6 @@ const roundToPageSize = v => (v + PAGE_SIZE-1) & ~(PAGE_SIZE-1);
                 }
                 newBuf = new Uint8Array(this.wasmMemory.buffer);
             }
-            newBuf.set(this.buf8.subarray(0, this.buf32[TRIE1_SLOT]), 0);
-            newBuf.set(
-                this.buf8.subarray(
-                    this.buf32[CHAR0_SLOT],
-                    this.buf32[CHAR1_SLOT]
-                ),
-                char0
-            );
             this.buf8 = newBuf;
             this.buf32 = new Uint32Array(this.buf8.buffer);
             this.buf32[CHAR0_SLOT] = char0;