[llvm] dfeb978 - Fixed a roll-over on size_t in getNewUninitMemBuffer()

[Dmitry Vassiliev via llvm-commits]

Author: Dmitry Vassiliev
Date: 2022-03-11T13:16:58+04:00
New Revision: dfeb9781557ca655bb99a31f4bcf4d0187d7dd38

URL: https://github.com/llvm/llvm-project/commit/dfeb9781557ca655bb99a31f4bcf4d0187d7dd38
DIFF: https://github.com/llvm/llvm-project/commit/dfeb9781557ca655bb99a31f4bcf4d0187d7dd38.diff

LOG: Fixed a roll-over on size_t in getNewUninitMemBuffer()

Reviewed By: serge-sans-paille

Differential Revision: https://reviews.llvm.org/D121399

Added: 
    

Modified: 
    llvm/lib/Support/MemoryBuffer.cpp
    llvm/unittests/Support/MemoryBufferTest.cpp

Removed: 
    


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diff  --git a/llvm/lib/Support/MemoryBuffer.cpp b/llvm/lib/Support/MemoryBuffer.cpp
index 5003822d9086a..872b874be34f4 100644
--- a/llvm/lib/Support/MemoryBuffer.cpp
+++ b/llvm/lib/Support/MemoryBuffer.cpp
@@ -286,6 +286,8 @@ WritableMemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName
   StringRef NameRef = BufferName.toStringRef(NameBuf);
   size_t AlignedStringLen = alignTo(sizeof(MemBuffer) + NameRef.size() + 1, 16);
   size_t RealLen = AlignedStringLen + Size + 1;
+  if (RealLen <= Size) // Check for rollover.
+    return nullptr;
   char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
   if (!Mem)
     return nullptr;

diff  --git a/llvm/unittests/Support/MemoryBufferTest.cpp b/llvm/unittests/Support/MemoryBufferTest.cpp
index bcd25021b5635..423d8f7611811 100644
--- a/llvm/unittests/Support/MemoryBufferTest.cpp
+++ b/llvm/unittests/Support/MemoryBufferTest.cpp
@@ -219,6 +219,11 @@ TEST_F(MemoryBufferTest, make_new) {
   EXPECT_NE(nullptr, Four.get());
   for (size_t i = 0; i < 123; ++i)
     EXPECT_EQ(0, Four->getBufferStart()[0]);
+
+  // uninitialized buffer with rollover size
+  OwningBuffer Five(
+      WritableMemoryBuffer::getNewUninitMemBuffer(SIZE_MAX, "huge"));
+  EXPECT_EQ(nullptr, Five.get());
 }
 
 void MemoryBufferTest::testGetOpenFileSlice(bool Reopen) {