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dqn: Add first draft of use-after-free in arenas

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This commit is contained in:
doyle 2023-06-01 00:00:33 +10:00
parent 558acd19e0
commit 8504cbff3a
3 changed files with 213 additions and 32 deletions
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212
dqn.h
View File

@ -4,7 +4,7 @@
// =================================================================================================
// Table Of Contents | Compile out with #define | Description
// =================================================================================================
// [$CFgM] Config macros | | Compile time customisation of library
// [$CFGM] Config macros | | Compile time customisation of library
// [$CMAC] Compiler macros | | Macros for the compiler
// [$INCL] Include files | | Standard library Include dependencies
// [$MACR] Macros | | Define macros used in the library
@ -139,10 +139,11 @@
#define Dqn_PowerOfTwoAlign(value, power_of_two) (((value) + ((power_of_two) - 1)) & ~((power_of_two) - 1))
#define Dqn_IsPowerOfTwo(value) (((value) & (value - 1)) == 0)
#define Dqn_IsPowerOfTwoAligned(value, power_of_two) (((value) & (power_of_two - 1)) == 0)
// NOTE: Alloc Macros ==============================================================================
#if !defined(DQN_ALLOC)
#define DQN_ALLOC(size) Dqn_VMem_Reserve(size, Dqn_VMemCommit_Yes)
#define DQN_ALLOC(size) Dqn_VMem_Reserve(size, Dqn_VMemCommit_Yes, Dqn_VMemPage_ReadWrite)
#endif
#if !defined(DQN_DEALLOC)
@ -1317,17 +1318,42 @@ DQN_API void Dqn_Log_FCallSite (Dqn_String8 type, Dqn_CallSite call_site, ch
// =================================================================================================
// [$VMEM] Dqn_VMem | | Virtual memory allocation
// =================================================================================================
enum Dqn_VMemCommit {
enum Dqn_VMemCommit
{
Dqn_VMemCommit_No,
Dqn_VMemCommit_Yes,
};
enum Dqn_VMemPage
{
/// Exception on read/write with a page. This flag overrides the read/write access.
Dqn_VMemPage_NoAccess = 1 << 0,
/// Only read permitted on the page.
Dqn_VMemPage_Read = 1 << 1,
/// Only write permitted on the page. On Windows this is not supported and will be promoted to
/// read+write permissions.
Dqn_VMemPage_Write = 1 << 2,
Dqn_VMemPage_ReadWrite = Dqn_VMemPage_Read | Dqn_VMemPage_Write,
/// Modifier used in conjunction with previous flags. This flag is *only* supported on Windows
/// ignored in other OS's. Exception on first access to the page, then, the underlying
/// protection flags are active.
Dqn_VMemPage_Guard = 1 << 3,
};
#if !defined(DQN_VMEM_PAGE_GRANULARITY)
#define DQN_VMEM_PAGE_GRANULARITY DQN_KILOBYTES(4)
#endif
#if !defined(DQN_VMEM_RESERVE_GRANULARITY)
#define DQN_VMEM_RESERVE_GRANULARITY DQN_KILOBYTES(64)
#endif
#if !defined(DQN_VMEM_COMMIT_GRANULARITY)
#define DQN_VMEM_COMMIT_GRANULARITY DQN_KILOBYTES(4)
#define DQN_VMEM_COMMIT_GRANULARITY DQN_VMEM_PAGE_GRANULARITY
#endif
static_assert(Dqn_IsPowerOfTwo(DQN_VMEM_RESERVE_GRANULARITY),
@ -1337,10 +1363,11 @@ static_assert(Dqn_IsPowerOfTwo(DQN_VMEM_COMMIT_GRANULARITY),
static_assert(DQN_VMEM_COMMIT_GRANULARITY < DQN_VMEM_RESERVE_GRANULARITY,
"Minimum commit size must be lower than the reserve size to avoid OOB math on pointers in this library");
DQN_API void *Dqn_VMem_Reserve(Dqn_usize size, Dqn_VMemCommit commit);
DQN_API bool Dqn_VMem_Commit(void *ptr, Dqn_usize size);
DQN_API void Dqn_VMem_Decommit(void *ptr, Dqn_usize size);
DQN_API void Dqn_VMem_Release(void *ptr, Dqn_usize size);
DQN_API void *Dqn_VMem_Reserve (Dqn_usize size, Dqn_VMemCommit commit, uint32_t page_flags);
DQN_API bool Dqn_VMem_Commit (void *ptr, Dqn_usize size);
DQN_API void Dqn_VMem_Decommit(void *ptr, Dqn_usize size);
DQN_API void Dqn_VMem_Release (void *ptr, Dqn_usize size);
DQN_API int Dqn_VMem_Protect (void *ptr, Dqn_usize size, uint32_t page_flags);
// =================================================================================================
// [$AREN] Dqn_Arena | | Growing bump allocator
@ -1426,7 +1453,8 @@ DQN_API void Dqn_VMem_Release(void *ptr, Dqn_usize size);
enum Dqn_ArenaBlockFlags
{
Dqn_ArenaBlockFlags_Private = 1 << 0, ///< Private blocks can only allocate its memory when used in the 'FromBlock' API variants
Dqn_ArenaBlockFlags_Private = 1 << 0, ///< Private blocks can only allocate its memory when used in the 'FromBlock' API variants
Dqn_ArenaBlockFlags_UseAfterFreeGuard = 1 << 1, ///< Pages guards are placed on freed memory ranges
};
struct Dqn_ArenaStat
@ -1464,6 +1492,8 @@ struct Dqn_ArenaStatString
struct Dqn_Arena
{
bool use_after_free_guard;
Dqn_String8 label; ///< Optional label to describe the arena
Dqn_usize min_block_size;
Dqn_ArenaBlock *curr; ///< The current memory block of the arena
@ -4464,7 +4494,10 @@ Dqn_BinarySearch(T const *array,
#define MEM_RELEASE 0x00008000
// NOTE: Protect
#define PAGE_NOACCESS 0x01
#define PAGE_READONLY 0x02
#define PAGE_READWRITE 0x04
#define PAGE_GUARD 0x100
// NOTE: FindFirstFile
#define INVALID_HANDLE_VALUE ((void *)(long *)-1)
@ -4996,16 +5029,57 @@ DQN_API void Dqn_Log_TypeFCallSite(Dqn_LogType type, Dqn_CallSite call_site, cha
// NOTE: Dqn_VMem_
// -------------------------------------------------------------------------------------------------
DQN_API void *Dqn_VMem_Reserve(Dqn_usize size, Dqn_VMemCommit commit)
DQN_FILE_SCOPE uint32_t Dqn_VMem_ConvertPageToOSFlags_(uint32_t protect)
{
DQN_ASSERT((protect & ~(Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard)) == 0);
DQN_ASSERT(protect != 0);
uint32_t result = 0;
#if defined(DQN_OS_WIN32)
if (protect & Dqn_VMemPage_NoAccess) {
result = PAGE_NOACCESS;
} else {
if (protect & Dqn_VMemPage_ReadWrite) {
result = PAGE_READWRITE;
} else if (protect & Dqn_VMemPage_Read) {
result = PAGE_READONLY;
} else if (protect & Dqn_VMemPage_Write) {
Dqn_Log_WarningF("Windows does not support write-only pages, granting read+write access");
result = PAGE_READWRITE;
}
}
if (protect & Dqn_VMemPage_Guard)
result |= PAGE_GUARD;
DQN_ASSERTF(result != PAGE_GUARD, "Page guard is a modifier, you must also specify a page permission like read or/and write");
#else
if (protect & Dqn_VMemPage_NoAccess) {
result = PROT_NONE;
} else {
if (protect & Dqn_VMemPage_Read)
result = PROT_READ;
if (protect & Dqn_VMemPage_Write)
result = PROT_WRITE;
}
#endif
return result;
}
DQN_API void *Dqn_VMem_Reserve(Dqn_usize size, Dqn_VMemCommit commit, uint32_t page_flags)
{
unsigned long os_page_flags = Dqn_VMem_ConvertPageToOSFlags_(page_flags);
#if defined(DQN_OS_WIN32)
unsigned long flags = MEM_RESERVE | (commit == Dqn_VMemCommit_Yes ? MEM_COMMIT : 0);
void *result = VirtualAlloc(nullptr, size, flags, PAGE_READWRITE);
void *result = VirtualAlloc(nullptr, size, flags, os_page_flags);
#elif defined(DQN_OS_UNIX)
if (commit == Dqn_VMemCommit_Yes)
os_page_flags |= (PROT_READ | PROT_WRITE);
unsigned flags = PROT_NONE | (commit == Dqn_VMemCommit_Yes ? (PROT_READ | PROT_WRITE) : 0);
void *result = mmap(nullptr, size, flags, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
void *result = mmap(nullptr, size, os_page_flags, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (result == MAP_FAILED)
result = nullptr;
@ -5051,6 +5125,28 @@ DQN_API void Dqn_VMem_Release(void *ptr, Dqn_usize size)
#endif
}
DQN_API int Dqn_VMem_Protect(void *ptr, Dqn_usize size, uint32_t page_flags)
{
if (!ptr || size == 0)
return 0;
unsigned long os_page_flags = Dqn_VMem_ConvertPageToOSFlags_(page_flags);
#if defined(DQN_OS_WIN32)
unsigned long prev_flags = 0;
int result = VirtualProtect(ptr, size, os_page_flags, &prev_flags);
(void)prev_flags;
if (result == 0) {
Dqn_WinErrorMsg error = Dqn_Win_LastError();
DQN_ASSERTF(result, "VirtualProtect failed (%d): %.*s", error.code, error.size, error.data);
}
#else
int result = mprotect(result->memory, result->size, os_page_flags);
DQN_ASSERTF(result == 0, "mprotect failed (%d)", errno);
#endif
return result;
}
// =================================================================================================
// [$CSTR] Dqn_CString8 | | C-string helpers
// =================================================================================================
@ -6097,19 +6193,23 @@ Dqn_String8 Dqn_String8Builder_Build(Dqn_String8Builder const *builder, Dqn_Allo
// =================================================================================================
// [$AREN] Dqn_Arena | | Growing bump allocator
// =================================================================================================
DQN_FILE_SCOPE Dqn_String8 DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR =
DQN_STRING8("Use-after-free guard requires that all pointers are page aligned because we "
"can only guard memory at a multiple of the page boundary.");
DQN_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dqn_ArenaCommit commit)
{
Dqn_usize commit_size = 0;
switch (commit) {
case Dqn_ArenaCommit_GetNewPages: {
commit_size = Dqn_PowerOfTwoAlign(size, DQN_KILOBYTES(4));
commit_size = Dqn_PowerOfTwoAlign(size, DQN_VMEM_COMMIT_GRANULARITY);
} break;
case Dqn_ArenaCommit_EnsureSpace: {
DQN_ASSERT(block->commit >= block->used);
Dqn_usize const unused_commit_space = block->commit - block->used;
if (unused_commit_space < size)
commit_size = Dqn_PowerOfTwoAlign(size - unused_commit_space, DQN_KILOBYTES(4));
commit_size = Dqn_PowerOfTwoAlign(size - unused_commit_space, DQN_VMEM_COMMIT_GRANULARITY);
} break;
}
@ -6117,6 +6217,19 @@ DQN_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dq
char *commit_ptr = DQN_CAST(char *)block->memory + block->commit;
Dqn_VMem_Commit(commit_ptr, commit_size);
block->commit += commit_size;
DQN_ASSERTF(block->commit < block->size,
"Block size should be PoT aligned and its alignment should be greater than the commit granularity [block_size=%_$$d, block_commit=%_$$d]",
block->size, block->commit);
// NOTE: Guard new pages being allocated from the block
if (block->arena->use_after_free_guard) {
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)commit_ptr, DQN_VMEM_PAGE_GRANULARITY),
"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(commit_size, DQN_VMEM_PAGE_GRANULARITY),
"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
Dqn_VMem_Protect(commit_ptr, commit_size, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
}
}
}
@ -6124,6 +6237,10 @@ DQN_API void *Dqn_Arena_AllocateFromBlock(Dqn_ArenaBlock *block, Dqn_usize size,
{
if (!block)
return nullptr;
DQN_ASSERTF((align & (align - 1)) == 0, "Power of two alignment required");
align = DQN_MAX(align, 1);
DQN_ASSERT(block->hwm_used <= block->commit);
DQN_ASSERT(block->hwm_used >= block->used);
DQN_ASSERTF(block->commit >= block->used,
@ -6152,6 +6269,19 @@ DQN_API void *Dqn_Arena_AllocateFromBlock(Dqn_ArenaBlock *block, Dqn_usize size,
// NOTE: Ensure requested bytes are backed by physical pages from the OS
Dqn_Arena_CommitFromBlock(block, allocation_size, Dqn_ArenaCommit_EnsureSpace);
// NOTE: Unlock the pages requested
if (block->arena->use_after_free_guard) {
char const error_msg[] = "Use-after-free guard requires that all pointers are page aligned because we "
"can only guard memory at a multiple of the page boundary.";
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)result, DQN_VMEM_PAGE_GRANULARITY),
"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)allocation_size, DQN_VMEM_PAGE_GRANULARITY),
"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)block->used + allocation_size, DQN_VMEM_PAGE_GRANULARITY),
"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
Dqn_VMem_Protect(result, allocation_size, Dqn_VMemPage_ReadWrite);
}
// NOTE: Update arena
Dqn_Arena *arena = block->arena;
arena->stats.used += allocation_size;
@ -6329,15 +6459,20 @@ DQN_API Dqn_ArenaBlock *Dqn_Arena_Grow_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena
if (!arena || size == 0)
return nullptr;
Dqn_usize block_metadata_size = sizeof(Dqn_ArenaBlock);
if (arena->use_after_free_guard)
block_metadata_size = Dqn_PowerOfTwoAlign(block_metadata_size, DQN_VMEM_PAGE_GRANULARITY);
commit = DQN_MIN(commit, size);
Dqn_usize reserve_aligned = Dqn_PowerOfTwoAlign(size + sizeof(Dqn_ArenaBlock), DQN_VMEM_RESERVE_GRANULARITY);
Dqn_usize commit_aligned = Dqn_PowerOfTwoAlign(commit + sizeof(Dqn_ArenaBlock), DQN_VMEM_COMMIT_GRANULARITY);
Dqn_usize reserve_aligned = Dqn_PowerOfTwoAlign(size + block_metadata_size, DQN_VMEM_RESERVE_GRANULARITY);
Dqn_usize commit_aligned = Dqn_PowerOfTwoAlign(commit + block_metadata_size, DQN_VMEM_COMMIT_GRANULARITY);
DQN_ASSERT(commit_aligned < reserve_aligned);
// NOTE: If the commit amount is the same as reserve size we can save one
// syscall by asking the OS to reserve+commit in the same call.
Dqn_VMemCommit commit_on_reserve = reserve_aligned == commit_aligned ? Dqn_VMemCommit_Yes : Dqn_VMemCommit_No;
auto *result = DQN_CAST(Dqn_ArenaBlock *)Dqn_VMem_Reserve(reserve_aligned, commit_on_reserve);
uint32_t page_flags = Dqn_VMemPage_ReadWrite;
auto *result = DQN_CAST(Dqn_ArenaBlock *)Dqn_VMem_Reserve(reserve_aligned, commit_on_reserve, page_flags);
if (result) {
// NOTE: Commit the amount requested by the user if we did not commit
// on reserve the initial range.
@ -6353,12 +6488,16 @@ DQN_API Dqn_ArenaBlock *Dqn_Arena_Grow_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena
DQN_ASSERT(result->prev == nullptr);
// NOTE: Setup the block
result->size = reserve_aligned - sizeof(*result);
result->commit = commit_aligned - sizeof(*result);
result->memory = DQN_CAST(uint8_t *)result + sizeof(*result);
result->memory = DQN_CAST(uint8_t *)result + block_metadata_size;
result->size = reserve_aligned - block_metadata_size;
result->commit = commit_aligned - block_metadata_size;
result->flags = flags;
result->arena = arena;
// NOTE: Guard all the pages
if (arena->use_after_free_guard)
Dqn_VMem_Protect(result->memory, commit_aligned - block_metadata_size, page_flags | Dqn_VMemPage_Guard);
// NOTE: Attach the block to the arena
if (arena->tail) {
arena->tail->next = result;
@ -6386,19 +6525,32 @@ DQN_API Dqn_ArenaBlock *Dqn_Arena_Grow_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena
DQN_API void *Dqn_Arena_Allocate_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena, Dqn_usize size, uint8_t align, Dqn_ZeroMem zero_mem)
{
DQN_ASSERTF((align & (align - 1)) == 0, "Power of two alignment required");
while (arena->curr && (arena->curr->flags & Dqn_ArenaBlockFlags_Private))
arena->curr = arena->curr->next;
align = DQN_MAX(align, 1);
void *result = Dqn_Arena_AllocateFromBlock(arena->curr, size, align, zero_mem);
if (!result) {
Dqn_usize allocation_size = size + (align - 1);
if (Dqn_Arena_Grow(DQN_LEAK_TRACE_ARG arena, allocation_size, allocation_size /*commit*/, 0 /*flags*/)) {
result = Dqn_Arena_AllocateFromBlock(arena->curr, size, align, zero_mem);
if (arena->use_after_free_guard) {
size = Dqn_PowerOfTwoAlign(size, DQN_VMEM_PAGE_GRANULARITY);
align = 0;
}
void *result = nullptr;
for (; !result;) {
while (arena->curr && (arena->curr->flags & Dqn_ArenaBlockFlags_Private))
arena->curr = arena->curr->next;
if (!arena->curr) {
Dqn_usize allocation_size = size + (align - 1);
if (!Dqn_Arena_Grow(DQN_LEAK_TRACE_ARG arena, allocation_size, allocation_size /*commit*/, 0 /*flags*/)) {
break;
}
arena->curr = arena->tail;
}
result = Dqn_Arena_AllocateFromBlock(arena->curr, size, align, zero_mem);
}
if (result)
DQN_ASSERT((arena->curr->flags & Dqn_ArenaBlockFlags_Private) == 0);
return result;
}
@ -8469,7 +8621,7 @@ DQN_API char *Dqn_Win_NetHandlePumpToAllocCString(Dqn_WinNetHandle *handle, size
size_t total_size = 0;
Dqn_Win_NetChunk *first_chunk = nullptr;
for (Dqn_Win_NetChunk *last_chunk = nullptr;;) {
auto *chunk = DQN_CAST(Dqn_Win_NetChunk *)Dqn_VMem_Reserve(sizeof(Dqn_Win_NetChunk), Dqn_VMemCommit_Yes);
auto *chunk = DQN_CAST(Dqn_Win_NetChunk *)Dqn_VMem_Reserve(sizeof(Dqn_Win_NetChunk), Dqn_VMemCommit_Yes, Dqn_VMemPage_ReadWrite);
bool pump_result = Dqn_Win_NetHandlePump(handle, chunk->data, DQN_WIN_NET_HANDLE_DOWNLOAD_SIZE, &chunk->size);
if (chunk->size) {
total_size += chunk->size;
@ -8486,7 +8638,7 @@ DQN_API char *Dqn_Win_NetHandlePumpToAllocCString(Dqn_WinNetHandle *handle, size
break;
}
auto *result = DQN_CAST(char *)Dqn_VMem_Reserve(total_size * sizeof(char), Dqn_VMemCommit_Yes);
auto *result = DQN_CAST(char *)Dqn_VMem_Reserve(total_size * sizeof(char), Dqn_VMemCommit_Yes, Dqn_VMemPage_ReadWrite);
char *result_ptr = result;
for (Dqn_Win_NetChunk *chunk = first_chunk; chunk;) {
DQN_MEMCPY(result_ptr, chunk->data, chunk->size);

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dqn.rdbg
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33
dqn_unit_tests.cpp
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@ -37,16 +37,16 @@ Dqn_Tester TestArena()
DQN_TESTER_GROUP(test, "Dqn_Arena") {
DQN_TESTER_TEST("Reused memory is zeroed out") {
Dqn_Arena arena = {};
DQN_ARENA_TEMP_MEMORY_SCOPE(&arena);
// NOTE: Allocate 128 kilobytes, fill it with garbage, then reset the arena
Dqn_usize size = DQN_KILOBYTES(128);
uintptr_t first_ptr_address = 0;
{
DQN_ARENA_TEMP_MEMORY_SCOPE(&arena);
Dqn_ArenaTempMemory temp_mem = Dqn_Arena_BeginTempMemory(&arena);
void *ptr = Dqn_Arena_Allocate(&arena, size, 1, Dqn_ZeroMem_Yes);
first_ptr_address = DQN_CAST(uintptr_t)ptr;
DQN_MEMSET(ptr, 'z', size);
Dqn_Arena_EndTempMemory(temp_mem);
}
// NOTE: Reallocate 128 kilobytes
@ -58,6 +58,35 @@ Dqn_Tester TestArena()
// NOTE: Check that the bytes are set to 0
for (Dqn_usize i = 0; i < size; i++)
DQN_TESTER_ASSERT(&test, ptr[i] == 0);
Dqn_Arena_Free(&arena, Dqn_ZeroMem_No);
}
Dqn_usize sizes[] = {DQN_KILOBYTES(1), DQN_KILOBYTES(4), DQN_KILOBYTES(5)};
for (Dqn_usize size : sizes) {
DQN_TESTER_TEST("Use-after-free guard on %.1f KiB allocation", size / 1024.0) {
Dqn_Arena arena = {};
arena.use_after_free_guard = true;
// NOTE: Wrap in temp memory, allocate and write
Dqn_ArenaTempMemory temp_mem = Dqn_Arena_BeginTempMemory(&arena);
Dqn_usize size = DQN_KILOBYTES(1);
uintptr_t first_ptr_address = 0;
void *ptr = Dqn_Arena_Allocate(&arena, size, 1, Dqn_ZeroMem_Yes);
DQN_MEMSET(ptr, 'z', size);
Dqn_Arena_EndTempMemory(temp_mem);
// NOTE: Temp memory is ended, try and write the pointer
// we should trigger the use-after-free guard.
bool caught = false;
__try {
DQN_MEMSET(ptr, 'a', size);
} __except (1) {
caught = true;
}
DQN_TESTER_ASSERTF(&test, caught, "Exception was not triggered, was page protected properly?");
Dqn_Arena_Free(&arena, Dqn_ZeroMem_No);
}
}
}