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dqn: Reguard pages on arena memory pop

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This commit is contained in:
doyle 2023-06-01 22:54:43 +10:00
parent adb429babd
commit d9a19fd742
3 changed files with 47 additions and 42 deletions
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83
dqn.h
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@ -1338,9 +1338,9 @@ enum Dqn_VMemPage
Dqn_VMemPage_ReadWrite = Dqn_VMemPage_Read | Dqn_VMemPage_Write, Dqn_VMemPage_ReadWrite = Dqn_VMemPage_Read | Dqn_VMemPage_Write,
/// Modifier used in conjunction with previous flags. This flag is *only* supported on Windows /// Modifier used in conjunction with previous flags. Raises exception on first access to the
/// ignored in other OS's. Exception on first access to the page, then, the underlying /// page, then, the underlying protection flags are active. This is supported on Windows, on
/// protection flags are active. /// other OS's using this flag will set the OS equivalent of Dqn_VMemPage_NoAccess.
Dqn_VMemPage_Guard = 1 << 3, Dqn_VMemPage_Guard = 1 << 3,
}; };
@ -1364,7 +1364,7 @@ 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"); "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, uint32_t page_flags); 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 bool Dqn_VMem_Commit (void *ptr, Dqn_usize size, uint32_t page_flags);
DQN_API void Dqn_VMem_Decommit(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_Release (void *ptr, Dqn_usize size);
DQN_API int Dqn_VMem_Protect (void *ptr, Dqn_usize size, uint32_t page_flags); DQN_API int Dqn_VMem_Protect (void *ptr, Dqn_usize size, uint32_t page_flags);
@ -1453,8 +1453,7 @@ DQN_API int Dqn_VMem_Protect (void *ptr, Dqn_usize size, uint32_t page_flags);
enum Dqn_ArenaBlockFlags 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 struct Dqn_ArenaStat
@ -5053,7 +5052,7 @@ DQN_FILE_SCOPE uint32_t Dqn_VMem_ConvertPageToOSFlags_(uint32_t protect)
DQN_ASSERTF(result != PAGE_GUARD, "Page guard is a modifier, you must also specify a page permission like read or/and write"); DQN_ASSERTF(result != PAGE_GUARD, "Page guard is a modifier, you must also specify a page permission like read or/and write");
#else #else
if (protect & Dqn_VMemPage_NoAccess) { if (protect & (Dqn_VMemPage_NoAccess | Dqn_VMemPage_Guard)) {
result = PROT_NONE; result = PROT_NONE;
} else { } else {
if (protect & Dqn_VMemPage_Read) if (protect & Dqn_VMemPage_Read)
@ -5088,12 +5087,13 @@ DQN_API void *Dqn_VMem_Reserve(Dqn_usize size, Dqn_VMemCommit commit, uint32_t p
return result; return result;
} }
DQN_API bool Dqn_VMem_Commit(void *ptr, Dqn_usize size) DQN_API bool Dqn_VMem_Commit(void *ptr, Dqn_usize size, uint32_t page_flags)
{ {
unsigned long os_page_flags = Dqn_VMem_ConvertPageToOSFlags_(page_flags);
#if defined(DQN_OS_WIN32) #if defined(DQN_OS_WIN32)
bool result = VirtualAlloc(ptr, size, MEM_COMMIT, PAGE_READWRITE) != nullptr; bool result = VirtualAlloc(ptr, size, MEM_COMMIT, os_page_flags) != nullptr;
#elif defined(DQN_OS_UNIX) #elif defined(DQN_OS_UNIX)
bool result = mprotect(ptr, size, PROT_READ|PROT_WRITE) == 0; bool result = mprotect(ptr, size, os_page_flags) == 0;
#else #else
#error "Missing implementation for Dqn_VMem_Commit" #error "Missing implementation for Dqn_VMem_Commit"
#endif #endif
@ -5129,6 +5129,12 @@ DQN_API int Dqn_VMem_Protect(void *ptr, Dqn_usize size, uint32_t page_flags)
if (!ptr || size == 0) if (!ptr || size == 0)
return 0; return 0;
static Dqn_String8 const ALIGNMENT_ERROR_MSG =
DQN_STRING8("Page protection requires pointers to be page aligned because we "
"can only guard memory at a multiple of the page boundary.");
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)ptr, DQN_VMEM_PAGE_GRANULARITY), "%s", ALIGNMENT_ERROR_MSG.data);
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(size, DQN_VMEM_PAGE_GRANULARITY), "%s", ALIGNMENT_ERROR_MSG.data);
unsigned long os_page_flags = Dqn_VMem_ConvertPageToOSFlags_(page_flags); unsigned long os_page_flags = Dqn_VMem_ConvertPageToOSFlags_(page_flags);
#if defined(DQN_OS_WIN32) #if defined(DQN_OS_WIN32)
unsigned long prev_flags = 0; unsigned long prev_flags = 0;
@ -6192,10 +6198,6 @@ Dqn_String8 Dqn_String8Builder_Build(Dqn_String8Builder const *builder, Dqn_Allo
// ================================================================================================= // =================================================================================================
// [$AREN] Dqn_Arena | | Growing bump allocator // [$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_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dqn_ArenaCommit commit)
{ {
Dqn_usize commit_size = 0; Dqn_usize commit_size = 0;
@ -6213,8 +6215,9 @@ DQN_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dq
} }
if (commit_size) { if (commit_size) {
uint32_t page_flags = Dqn_VMemPage_ReadWrite;
char *commit_ptr = DQN_CAST(char *)block->memory + block->commit; char *commit_ptr = DQN_CAST(char *)block->memory + block->commit;
Dqn_VMem_Commit(commit_ptr, commit_size); Dqn_VMem_Commit(commit_ptr, commit_size, page_flags);
block->commit += commit_size; block->commit += commit_size;
DQN_ASSERTF(block->commit < block->size, DQN_ASSERTF(block->commit < block->size,
@ -6222,13 +6225,8 @@ DQN_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dq
block->size, block->commit); block->size, block->commit);
// NOTE: Guard new pages being allocated from the block // NOTE: Guard new pages being allocated from the block
if (block->arena->use_after_free_guard) { if (block->arena->use_after_free_guard)
DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)commit_ptr, DQN_VMEM_PAGE_GRANULARITY), Dqn_VMem_Protect(commit_ptr, commit_size, page_flags | Dqn_VMemPage_Guard);
"%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);
}
} }
} }
@ -6269,17 +6267,8 @@ DQN_API void *Dqn_Arena_AllocateFromBlock(Dqn_ArenaBlock *block, Dqn_usize size,
Dqn_Arena_CommitFromBlock(block, allocation_size, Dqn_ArenaCommit_EnsureSpace); Dqn_Arena_CommitFromBlock(block, allocation_size, Dqn_ArenaCommit_EnsureSpace);
// NOTE: Unlock the pages requested // NOTE: Unlock the pages requested
if (block->arena->use_after_free_guard) { 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); Dqn_VMem_Protect(result, allocation_size, Dqn_VMemPage_ReadWrite);
}
// NOTE: Update arena // NOTE: Update arena
Dqn_Arena *arena = block->arena; Dqn_Arena *arena = block->arena;
@ -6338,7 +6327,12 @@ DQN_API void Dqn_Arena_Reset(Dqn_Arena *arena, Dqn_ZeroMem zero_mem)
arena->curr = block; arena->curr = block;
if (zero_mem == Dqn_ZeroMem_Yes) if (zero_mem == Dqn_ZeroMem_Yes)
DQN_MEMSET(block->memory, DQN_MEMSET_BYTE, block->commit); DQN_MEMSET(block->memory, DQN_MEMSET_BYTE, block->commit);
block->used = 0; block->used = 0;
// NOTE: Guard all the committed pages again
if (arena->use_after_free_guard)
Dqn_VMem_Protect(block->memory, block->commit, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
} }
arena->stats.used = 0; arena->stats.used = 0;
@ -6370,8 +6364,14 @@ DQN_API void Dqn_Arena_EndTempMemory_(DQN_LEAK_TRACE_FUNCTION Dqn_ArenaTempMemor
// NOTE: Revert the current block to the scope's current block // NOTE: Revert the current block to the scope's current block
arena->curr = scope.curr; arena->curr = scope.curr;
if (arena->curr) if (arena->curr) {
arena->curr->used = scope.curr_used; Dqn_ArenaBlock *curr = arena->curr;
curr->used = scope.curr_used;
// NOTE: Reguard the pages
if (arena->use_after_free_guard)
Dqn_VMem_Protect(curr->memory, curr->commit, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
}
// NOTE: Free the tail blocks until we reach the scope's tail block // NOTE: Free the tail blocks until we reach the scope's tail block
while (arena->tail != scope.tail) { while (arena->tail != scope.tail) {
@ -6384,8 +6384,13 @@ DQN_API void Dqn_Arena_EndTempMemory_(DQN_LEAK_TRACE_FUNCTION Dqn_ArenaTempMemor
// NOTE: Reset the usage of all the blocks between the tail and current block's // NOTE: Reset the usage of all the blocks between the tail and current block's
if (arena->tail) { if (arena->tail) {
arena->tail->next = nullptr; arena->tail->next = nullptr;
for (Dqn_ArenaBlock *block = arena->tail; block && block != arena->curr; block = block->prev) for (Dqn_ArenaBlock *block = arena->tail; block && block != arena->curr; block = block->prev) {
block->used = 0; block->used = 0;
// NOTE: Reguard the pages
if (arena->use_after_free_guard)
Dqn_VMem_Protect(block->memory, block->commit, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
}
} }
} }
@ -6476,7 +6481,7 @@ DQN_API Dqn_ArenaBlock *Dqn_Arena_Grow_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena
// NOTE: Commit the amount requested by the user if we did not commit // NOTE: Commit the amount requested by the user if we did not commit
// on reserve the initial range. // on reserve the initial range.
if (commit_on_reserve == Dqn_VMemCommit_No) { if (commit_on_reserve == Dqn_VMemCommit_No) {
Dqn_VMem_Commit(result, commit_aligned); Dqn_VMem_Commit(result, commit_aligned, page_flags);
} else { } else {
DQN_ASSERT(commit_aligned == reserve_aligned); DQN_ASSERT(commit_aligned == reserve_aligned);
} }
@ -6493,9 +6498,9 @@ DQN_API Dqn_ArenaBlock *Dqn_Arena_Grow_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena
result->flags = flags; result->flags = flags;
result->arena = arena; result->arena = arena;
// NOTE: Guard all the pages // NOTE: Guard all the committed pages in the memory block
if (arena->use_after_free_guard) if (arena->use_after_free_guard)
Dqn_VMem_Protect(result->memory, commit_aligned - block_metadata_size, page_flags | Dqn_VMemPage_Guard); Dqn_VMem_Protect(result->memory, result->commit, page_flags | Dqn_VMemPage_Guard);
// NOTE: Attach the block to the arena // NOTE: Attach the block to the arena
if (arena->tail) { if (arena->tail) {
@ -6528,7 +6533,7 @@ DQN_API void *Dqn_Arena_Allocate_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena, Dqn_
if (arena->use_after_free_guard) { if (arena->use_after_free_guard) {
size = Dqn_PowerOfTwoAlign(size, DQN_VMEM_PAGE_GRANULARITY); size = Dqn_PowerOfTwoAlign(size, DQN_VMEM_PAGE_GRANULARITY);
align = 0; align = 1;
} }
void *result = nullptr; void *result = nullptr;

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dqn.rdbg
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6
dqn_unit_tests.cpp
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@ -66,12 +66,12 @@ Dqn_Tester TestArena()
DQN_TESTER_TEST("Use-after-free guard on %.1f KiB allocation", size / 1024.0) { DQN_TESTER_TEST("Use-after-free guard on %.1f KiB allocation", size / 1024.0) {
Dqn_Arena arena = {}; Dqn_Arena arena = {};
arena.use_after_free_guard = true; arena.use_after_free_guard = true;
Dqn_Arena_Grow(&arena, size, false /*commit*/, 0 /*flags*/);
// NOTE: Wrap in temp memory, allocate and write // NOTE: Wrap in temp memory, allocate and write
Dqn_ArenaTempMemory temp_mem = Dqn_Arena_BeginTempMemory(&arena); Dqn_ArenaTempMemory temp_mem = Dqn_Arena_BeginTempMemory(&arena);
Dqn_usize size = DQN_KILOBYTES(1); uintptr_t first_ptr_address = 0;
uintptr_t first_ptr_address = 0; void *ptr = Dqn_Arena_Allocate(&arena, size, 1, Dqn_ZeroMem_Yes);
void *ptr = Dqn_Arena_Allocate(&arena, size, 1, Dqn_ZeroMem_Yes);
DQN_MEMSET(ptr, 'z', size); DQN_MEMSET(ptr, 'z', size);
Dqn_Arena_EndTempMemory(temp_mem); Dqn_Arena_EndTempMemory(temp_mem);