From e2825f8e279c93ba66105fab8b2b8a488d4e7c08 Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Thu, 6 Aug 2015 16:02:17 +0000 Subject: [PATCH] Merging r243927, r243932, and r243934: ------------------------------------------------------------------------ r243927 | chandlerc | 2015-08-03 17:44:07 -0700 (Mon, 03 Aug 2015) | 11 lines [UB] Fix a nasty place where we would pass null pointers to memcpy. This happens to work, but is not guaranteed to work. Indeed, most memcpy interfaces in Linux-land annotate these arguments as nonnull, and GCC and LLVM both can and do optimized based upon that. When they do so, they might legitimately have miscompiled code calling this routine with two valid iterators, 'nullptr' and 'nullptr'. There was even code doing precisely this because StringRef().begin() and StringRef().end() both produce null pointers. This was found by UBSan. ------------------------------------------------------------------------ ------------------------------------------------------------------------ r243932 | chandlerc | 2015-08-03 17:53:01 -0700 (Mon, 03 Aug 2015) | 3 lines [UB] Fix another place where we would pass a null pointer to memcpy. This too was found by UBSan. Down to 35 failures for me. ------------------------------------------------------------------------ ------------------------------------------------------------------------ r243934 | chandlerc | 2015-08-03 18:00:56 -0700 (Mon, 03 Aug 2015) | 4 lines [UB] Fix yet another use of memcpy with a null pointer argument. I think this is the last of them in my build of LLVM. Haven't tried Clang yet. Found via UBSan. ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_37@244224 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/ADT/SmallVector.h | 6 ++++-- include/llvm/ADT/StringMap.h | 3 ++- lib/Support/MemoryBuffer.cpp | 3 ++- 3 files changed, 8 insertions(+), 4 deletions(-) diff --git a/include/llvm/ADT/SmallVector.h b/include/llvm/ADT/SmallVector.h index 5b208b76a21..b9384702c3b 100644 --- a/include/llvm/ADT/SmallVector.h +++ b/include/llvm/ADT/SmallVector.h @@ -315,8 +315,10 @@ protected: T2>::value>::type * = nullptr) { // Use memcpy for PODs iterated by pointers (which includes SmallVector // iterators): std::uninitialized_copy optimizes to memmove, but we can - // use memcpy here. - memcpy(Dest, I, (E-I)*sizeof(T)); + // use memcpy here. Note that I and E are iterators and thus might be + // invalid for memcpy if they are equal. + if (I != E) + memcpy(Dest, I, (E - I) * sizeof(T)); } /// Double the size of the allocated memory, guaranteeing space for at diff --git a/include/llvm/ADT/StringMap.h b/include/llvm/ADT/StringMap.h index 8721c73b95b..9d038560bf9 100644 --- a/include/llvm/ADT/StringMap.h +++ b/include/llvm/ADT/StringMap.h @@ -158,7 +158,8 @@ public: // Copy the string information. char *StrBuffer = const_cast(NewItem->getKeyData()); - memcpy(StrBuffer, Key.data(), KeyLength); + if (KeyLength > 0) + memcpy(StrBuffer, Key.data(), KeyLength); StrBuffer[KeyLength] = 0; // Null terminate for convenience of clients. return NewItem; } diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp index 98862e96b74..d09ef3a4c0b 100644 --- a/lib/Support/MemoryBuffer.cpp +++ b/lib/Support/MemoryBuffer.cpp @@ -57,7 +57,8 @@ void MemoryBuffer::init(const char *BufStart, const char *BufEnd, /// CopyStringRef - Copies contents of a StringRef into a block of memory and /// null-terminates it. static void CopyStringRef(char *Memory, StringRef Data) { - memcpy(Memory, Data.data(), Data.size()); + if (!Data.empty()) + memcpy(Memory, Data.data(), Data.size()); Memory[Data.size()] = 0; // Null terminate string. } -- 2.40.0