zlib: fix pointer alignment

The function AllocForBrotli prefixes the allocated memory with its size, and returns a pointer to the region after it. This pointer can however no longer be suitably aligned. Correct this by allocating the maximum of the the size of the size_t and the max alignment. On Arm 32bits the size_t is 4 bytes long, but the alignment is 8 for some NEON instructions. When Brotli is compiled with optimizations enabled newer GCC versions will use the NEON instructions and trigger a bus error killing node. see google/brotli#1159 PR-URL: #57727 Reviewed-By: Shelley Vohr <shelley.vohr@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Daniel Lemire <daniel@lemire.me> Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

Author: jhofstee

src/node_zlib.cc

@@ -493,20 +493,22 @@ class CompressionStream : public AsyncWrap, public ThreadPoolWork {
  }
 
  static void* AllocForBrotli(void* data, size_t size) {
- size += sizeof(size_t);
+ constexpr size_t offset = std::max(sizeof(size_t), alignof(max_align_t));
+ size += offset;
  CompressionStream* ctx = static_cast<CompressionStream*>(data);
  char* memory = UncheckedMalloc(size);
  if (UNLIKELY(memory == nullptr)) return nullptr;
  *reinterpret_cast<size_t*>(memory) = size;
  ctx->unreported_allocations_.fetch_add(size,
  std::memory_order_relaxed);
- return memory + sizeof(size_t);
+ return memory + offset;
  }
 
  static void FreeForZlib(void* data, void* pointer) {
  if (UNLIKELY(pointer == nullptr)) return;
  CompressionStream* ctx = static_cast<CompressionStream*>(data);
- char* real_pointer = static_cast<char*>(pointer) - sizeof(size_t);
+ constexpr size_t offset = std::max(sizeof(size_t), alignof(max_align_t));
+ char* real_pointer = static_cast<char*>(pointer) - offset;
  size_t real_size = *reinterpret_cast<size_t*>(real_pointer);
  ctx->unreported_allocations_.fetch_sub(real_size,
  std::memory_order_relaxed);