qUncompress: limit MaxDecompressedSize to what zlib can handle

... which may be less than what QByteArray can handle, e.g. on Windows,
where long, used in the zlib API as the size type, is just 32-bit.

Re-define MaxDecompressedSize as the minimum of the maximum sizes
supported by each of QByteArray and zlib, so we respect each library's
individual limit.

Pick-to: 6.4 6.3 6.2
Task-number: QTBUG-104972
Change-Id: If1894ae7a1888f651a82b153d463658c272287e3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index 8d552b7fd0..6e65b06f65 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -632,7 +632,8 @@ QByteArray qUncompress(const uchar* data, qsizetype nbytes)
     size_t expectedSize = size_t((data[0] << 24) | (data[1] << 16) |
                                  (data[2] <<  8) | (data[3]      ));
     size_t len = qMax(expectedSize, 1ul);
-    constexpr size_t MaxDecompressedSize = size_t(MaxByteArraySize);
+    constexpr size_t MaxZLibSize = (std::numeric_limits<uLong>::max)();
+    constexpr size_t MaxDecompressedSize = (std::min)(size_t(MaxByteArraySize), MaxZLibSize);
     if (len > MaxDecompressedSize)
         return invalidCompressedData();