From 51ae5748cb790fa07cd4fd0ef55112dcc0338b52 Mon Sep 17 00:00:00 2001
From: bobsayshilol <bobsayshilol@live.co.uk>
Date: Sun, 25 Apr 2021 12:34:23 +0100
Subject: [PATCH] ID3v2: Return early from decode() on invalid data

The while loop in this function assumes that `data.end() - 1` is less
than `data.end()`, which isn't the case if `data` is empty since
`data.end()` can be a nullptr.
---
 taglib/mpeg/id3v2/id3v2synchdata.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/taglib/mpeg/id3v2/id3v2synchdata.cpp b/taglib/mpeg/id3v2/id3v2synchdata.cpp
index 2aa99999..ba848dec 100644
--- a/taglib/mpeg/id3v2/id3v2synchdata.cpp
+++ b/taglib/mpeg/id3v2/id3v2synchdata.cpp
@@ -74,6 +74,10 @@ ByteVector SynchData::fromUInt(unsigned int value)
 
 ByteVector SynchData::decode(const ByteVector &data)
 {
+  if (data.size() == 0) {
+    return ByteVector();
+  }
+
   // We have this optimized method instead of using ByteVector::replace(),
   // since it makes a great difference when decoding huge unsynchronized frames.