From 48ac38ec9b606844a346fb82b9101ba0c2d7be2b Mon Sep 17 00:00:00 2001
From: Mirko Bonadei <mbonadei@webrtc.org>
Date: Mon, 15 Aug 2022 08:20:44 +0000
Subject: [PATCH] Prevent UB on BufferT::AppendData.

As per https://en.cppreference.com/w/cpp/string/byte/memcpy, calling
std::memcpy with dest or src as nullptr is UB.

This CL prevents this from happening and is also looking into
why UBSan didn't catch the issue.

Bug: webrtc:14292
Change-Id: I99833f28ac865719d0dcb02c4de00f33a48c3992
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/271502
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37783}
---
 rtc_base/buffer.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/rtc_base/buffer.h b/rtc_base/buffer.h
index be8e22bf9f..819e7db3a6 100644
--- a/rtc_base/buffer.h
+++ b/rtc_base/buffer.h
@@ -267,6 +267,10 @@ class BufferT {
             typename std::enable_if<
                 internal::BufferCompat<T, U>::value>::type* = nullptr>
   void AppendData(const U* data, size_t size) {
+    if (!data) {
+      RTC_CHECK_EQ(size, 0U);
+      return;
+    }
     RTC_DCHECK(IsConsistent());
     const size_t new_size = size_ + size;
     EnsureCapacityWithHeadroom(new_size, true);