From 748a652f04cd3a202ce3639770238bd9473b300c Mon Sep 17 00:00:00 2001 From: Veselin Georgiev Date: Fri, 27 Jul 2018 13:33:09 -0500 Subject: [PATCH] Fix SIGBUS due to unaligned access Update RAPIDJSON_ALIGN() to always align on an 8-byte boundary unless otherwise overridden. On some platforms (such as ARM), 64-bit items (such as doubles and 64-bit integers) must be aligned to an 8 byte address, even though the architecture is only 32-bits. On these platforms, MemoryPoolAllocator must match the malloc() behavior and return a 8 byte aligned allocation. This eliminates any alignment issues that may occur at the expense of additional memory overhead. Failure to do so caused a SIGBUS signal when calling GenericValue::SetNull(). The size of the data_ member of the GenericValue class is 16 bytes in 32-bit mode and its constructor requires an 8-byte aligned access. While parsing a JSON formatted string using Document::ParseStream(), a stack object containing GenericValue items was constructed. Since the stack was 8-byte aligned, the constructor calls would succeed. When the lifetime of the object ends, SetObjectRaw() is invoked. This triggered an allocation with 4-byte alignment to which the previously 8-byte aligned GenericValue array was copied. After this, any call to a GenericValue API that triggered the constructor and thus the placement new operation on the Data type member would trigger a SIGBUS. Signed-off-by: Veselin Georgiev Signed-off-by: Joshua Watt Upstream-Status: Accepted 748a652f04cd3a202ce3639770238bd9473b300c --- include/rapidjson/rapidjson.h | 9 ++------- test/unittest/allocatorstest.cpp | 26 ++++++++++++-------------- 2 files changed, 14 insertions(+), 21 deletions(-) diff --git a/include/rapidjson/rapidjson.h b/include/rapidjson/rapidjson.h index a256c86e7..8cff38c2d 100644 --- a/include/rapidjson/rapidjson.h +++ b/include/rapidjson/rapidjson.h @@ -269,16 +269,11 @@ /*! \ingroup RAPIDJSON_CONFIG \param x pointer to align - Some machines require strict data alignment. Currently the default uses 4 bytes - alignment on 32-bit platforms and 8 bytes alignment for 64-bit platforms. + Some machines require strict data alignment. The default is 8 bytes. User can customize by defining the RAPIDJSON_ALIGN function macro. */ #ifndef RAPIDJSON_ALIGN -#if RAPIDJSON_64BIT == 1 -#define RAPIDJSON_ALIGN(x) (((x) + static_cast(7u)) & ~static_cast(7u)) -#else -#define RAPIDJSON_ALIGN(x) (((x) + 3u) & ~3u) -#endif +#define RAPIDJSON_ALIGN(x) (((x) + static_cast(7u)) & ~static_cast(7u)) #endif /////////////////////////////////////////////////////////////////////////////// diff --git a/test/unittest/allocatorstest.cpp b/test/unittest/allocatorstest.cpp index a5958de19..2202c11f6 100644 --- a/test/unittest/allocatorstest.cpp +++ b/test/unittest/allocatorstest.cpp @@ -63,23 +63,21 @@ TEST(Allocator, MemoryPoolAllocator) { } TEST(Allocator, Alignment) { -#if RAPIDJSON_64BIT == 1 - EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000000), RAPIDJSON_ALIGN(0)); - for (uint64_t i = 1; i < 8; i++) { - EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008), RAPIDJSON_ALIGN(i)); - EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000010), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008) + i)); - EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000001, 0x00000000), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0xFFFFFFF8) + i)); - EXPECT_EQ(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF8), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF0) + i)); + if (sizeof(size_t) >= 8) { + EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000000), RAPIDJSON_ALIGN(0)); + for (uint64_t i = 1; i < 8; i++) { + EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008), RAPIDJSON_ALIGN(i)); + EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000010), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008) + i)); + EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000001, 0x00000000), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0xFFFFFFF8) + i)); + EXPECT_EQ(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF8), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF0) + i)); + } } -#else + EXPECT_EQ(0u, RAPIDJSON_ALIGN(0u)); - for (uint32_t i = 1; i < 4; i++) { - EXPECT_EQ(4u, RAPIDJSON_ALIGN(i)); - EXPECT_EQ(8u, RAPIDJSON_ALIGN(4u + i)); - EXPECT_EQ(0xFFFFFFF8u, RAPIDJSON_ALIGN(0xFFFFFFF4u + i)); - EXPECT_EQ(0xFFFFFFFCu, RAPIDJSON_ALIGN(0xFFFFFFF8u + i)); + for (uint32_t i = 1; i < 8; i++) { + EXPECT_EQ(8u, RAPIDJSON_ALIGN(i)); + EXPECT_EQ(0xFFFFFFF8u, RAPIDJSON_ALIGN(0xFFFFFFF0u + i)); } -#endif } TEST(Allocator, Issue399) {