mirror of
https://github.com/microsoft/mimalloc.git
synced 2024-12-27 13:33:18 +08:00
enable double free and heap corruption detection in debug mode
This commit is contained in:
daan
parent
87bdfbb9b6
commit
b052d3b731
@ -379,7 +379,7 @@ static inline bool mi_is_in_same_segment(const void* p, const void* q) {
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}
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static inline mi_block_t* mi_block_nextx( uintptr_t cookie, const mi_block_t* block ) {
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#if MI_SECURE
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#ifdef MI_ENCODE_FREELIST
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return (mi_block_t*)(block->next ^ cookie);
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#else
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UNUSED(cookie);
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@ -388,7 +388,7 @@ static inline mi_block_t* mi_block_nextx( uintptr_t cookie, const mi_block_t* bl
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}
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static inline void mi_block_set_nextx(uintptr_t cookie, mi_block_t* block, const mi_block_t* next) {
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#if MI_SECURE
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#ifdef MI_ENCODE_FREELIST
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block->next = (mi_encoded_t)next ^ cookie;
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#else
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UNUSED(cookie);
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@ -397,16 +397,15 @@ static inline void mi_block_set_nextx(uintptr_t cookie, mi_block_t* block, const
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}
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static inline mi_block_t* mi_block_next(const mi_page_t* page, const mi_block_t* block) {
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#if MI_SECURE
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#ifdef MI_ENCODE_FREELIST
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mi_block_t* next = mi_block_nextx(page->cookie,block);
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#if MI_SECURE >= 4
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// check if next is at least in our segment range
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// TODO: it is better to check if it is actually inside our page but that is more expensive
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// to calculate. Perhaps with a relative free list this becomes feasible?
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if (next!=NULL && !mi_is_in_same_segment(block, next)) {
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_mi_fatal_error("corrupted free list entry at %p: %zx\n", block, (uintptr_t)next);
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}
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#endif
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// check for free list corruption: is `next` at least in our segment range?
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// TODO: it is better to check if it is actually inside our page but that is more expensive
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// to calculate. Perhaps with a relative free list this becomes feasible?
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if (next!=NULL && !mi_is_in_same_segment(block, next)) {
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_mi_fatal_error("corrupted free list entry of size %zub at %p: value 0x%zx\n", page->block_size, block, (uintptr_t)next);
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next = NULL;
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}
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return next;
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#else
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UNUSED(page);
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@ -415,7 +414,7 @@ static inline mi_block_t* mi_block_next(const mi_page_t* page, const mi_block_t*
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}
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static inline void mi_block_set_next(const mi_page_t* page, mi_block_t* block, const mi_block_t* next) {
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#if MI_SECURE
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#ifdef MI_ENCODE_FREELIST
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mi_block_set_nextx(page->cookie,block,next);
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#else
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UNUSED(page);
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@ -25,24 +25,30 @@ terms of the MIT license. A copy of the license can be found in the file
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// Define MI_SECURE to enable security mitigations
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// #define MI_SECURE 1 // guard page around metadata
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// #define MI_SECURE 2 // guard page around each mimalloc page
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// #define MI_SECURE 3 // encode free lists
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// #define MI_SECURE 4 // all security enabled (checks for double free, corrupted free list and invalid pointer free)
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// #define MI_SECURE 3 // encode free lists (detect corrupted free list (buffer overflow), and invalid pointer free)
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// #define MI_SECURE 4 // experimental, may be more expensive: checks for double free.
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#if !defined(MI_SECURE)
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#define MI_SECURE 0
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#endif
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// Define MI_DEBUG as 1 for basic assert checks and statistics
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// set it to 2 to do internal asserts,
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// and to 3 to do extensive invariant checking.
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// Define MI_DEBUG for debug mode
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// #define MI_DEBUG 1 // basic assertion checks and statistics, check double free, corrupted free list, and invalid pointer free.
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// #define MI_DEBUG 2 // + internal assertion checks
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// #define MI_DEBUG 3 // + extensive internal invariant checking
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#if !defined(MI_DEBUG)
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#if !defined(NDEBUG) || defined(_DEBUG)
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#define MI_DEBUG 1
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#define MI_DEBUG 2
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#else
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#define MI_DEBUG 0
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#endif
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#endif
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// Encoded free lists allow detection of corrupted free lists
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// and can detect buffer overflows and double `free`s.
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#if (MI_SECURE>=3 || MI_DEBUG>=1)
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#define MI_ENCODE_FREELIST 1
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#endif
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// ------------------------------------------------------
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// Platform specific values
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@ -117,6 +123,8 @@ terms of the MIT license. A copy of the license can be found in the file
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#error "define more bins"
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#endif
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// The free lists use encoded next fields
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// (Only actually encodes when MI_ENCODED_FREELIST is defined.)
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typedef uintptr_t mi_encoded_t;
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// free lists contain blocks
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@ -125,6 +133,7 @@ typedef struct mi_block_s {
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} mi_block_t;
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// The delayed flags are used for efficient multi-threaded free-ing
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typedef enum mi_delayed_e {
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MI_NO_DELAYED_FREE = 0,
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MI_USE_DELAYED_FREE = 1,
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@ -180,7 +189,7 @@ typedef struct mi_page_s {
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bool is_zero; // `true` if the blocks in the free list are zero initialized
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mi_block_t* free; // list of available free blocks (`malloc` allocates from this list)
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#if MI_SECURE
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#ifdef MI_ENCODE_FREELIST
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uintptr_t cookie; // random cookie to encode the free lists
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#endif
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size_t used; // number of blocks in use (including blocks in `local_free` and `thread_free`)
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@ -197,8 +206,8 @@ typedef struct mi_page_s {
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// improve page index calculation
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// without padding: 10 words on 64-bit, 11 on 32-bit. Secure adds one word
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#if (MI_INTPTR_SIZE==8 && MI_SECURE>0) || (MI_INTPTR_SIZE==4 && MI_SECURE==0)
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void* padding[1]; // 12 words on 64-bit in secure mode, 12 words on 32-bit plain
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#if (MI_INTPTR_SIZE==8 && defined(MI_ENCODE_FREELIST)) || (MI_INTPTR_SIZE==4 && !defined(MI_ENCODE_FREELIST))
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void* padding[1]; // 12 words on 64-bit with cookie, 12 words on 32-bit plain
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#endif
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} mi_page_t;
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47
src/alloc.c
47
src/alloc.c
@ -32,10 +32,10 @@ extern inline void* _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t siz
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page->free = mi_block_next(page,block);
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page->used++;
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mi_assert_internal(page->free == NULL || _mi_ptr_page(page->free) == page);
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#if (MI_DEBUG)
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#if (MI_DEBUG!=0)
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if (!page->is_zero) { memset(block, MI_DEBUG_UNINIT, size); }
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#elif (MI_SECURE)
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block->next = 0;
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#elif (MI_SECURE!=0)
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block->next = 0; // don't leak internal data
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#endif
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#if (MI_STAT>1)
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if(size <= MI_LARGE_OBJ_SIZE_MAX) {
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@ -125,10 +125,12 @@ mi_decl_allocator void* mi_zalloc(size_t size) mi_attr_noexcept {
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// ------------------------------------------------------
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// Check for double free in secure mode
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// Check for double free in secure and debug mode
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// This is somewhat expensive so only enabled for secure mode 4
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// ------------------------------------------------------
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#if MI_SECURE>=4
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#if (MI_ENCODE_FREELIST && (MI_SECURE>=4 || MI_DEBUG!=0))
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// linear check if the free list contains a specific element
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static bool mi_list_contains(const mi_page_t* page, const mi_block_t* list, const mi_block_t* elem) {
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while (list != NULL) {
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if (elem==list) return true;
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@ -137,15 +139,15 @@ static bool mi_list_contains(const mi_page_t* page, const mi_block_t* list, cons
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return false;
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}
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static mi_decl_noinline bool mi_check_double_freex(const mi_page_t* page, const mi_block_t* block, const mi_block_t* n) {
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static mi_decl_noinline bool mi_check_is_double_freex(const mi_page_t* page, const mi_block_t* block, const mi_block_t* n) {
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size_t psize;
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uint8_t* pstart = _mi_page_start(_mi_page_segment(page), page, &psize);
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if (n == NULL || ((uint8_t*)n >= pstart && (uint8_t*)n < (pstart + psize))) {
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// Suspicious: the decoded value is in the same page (or NULL).
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// Walk the free lists to see if it is already freed
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// Walk the free lists to verify positively if it is already freed
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if (mi_list_contains(page, page->free, block) ||
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mi_list_contains(page, page->local_free, block) ||
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mi_list_contains(page, (const mi_block_t*)mi_atomic_read_ptr_relaxed(mi_atomic_cast(void*,&page->thread_free)), block))
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mi_list_contains(page, page->local_free, block) ||
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mi_list_contains(page, (const mi_block_t*)mi_atomic_read_ptr_relaxed(mi_atomic_cast(void*,&page->thread_free)), block))
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{
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_mi_fatal_error("double free detected of block %p with size %zu\n", block, page->block_size);
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return true;
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@ -154,16 +156,23 @@ static mi_decl_noinline bool mi_check_double_freex(const mi_page_t* page, const
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return false;
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}
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static inline bool mi_check_double_free(const mi_page_t* page, const mi_block_t* block) {
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mi_block_t* n = (mi_block_t*)(block->next ^ page->cookie);
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if (((uintptr_t)n & (MI_INTPTR_SIZE-1))==0 && // quick check
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(n==NULL || mi_is_in_same_segment(block, n)))
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static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) {
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mi_block_t* n = mi_block_nextx(page->cookie, block); // pretend it is freed, and get the decoded first field
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if (((uintptr_t)n & (MI_INTPTR_SIZE-1))==0 && // quick check: aligned pointer?
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(n==NULL || mi_is_in_same_segment(block, n))) // quick check: in same segment or NULL?
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{
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// Suspicous: decoded value in block is in the same segment (or NULL) -- maybe a double free?
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return mi_check_double_freex(page, block, n);
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// (continue in separate function to improve code generation)
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return mi_check_is_double_freex(page, block, n);
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}
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return false;
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}
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#else
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static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) {
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UNUSED(page);
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UNUSED(block);
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return false;
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}
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#endif
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@ -171,7 +180,6 @@ static inline bool mi_check_double_free(const mi_page_t* page, const mi_block_t*
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// Free
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// ------------------------------------------------------
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// multi-threaded free
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static mi_decl_noinline void _mi_free_block_mt(mi_page_t* page, mi_block_t* block)
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{
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@ -258,6 +266,7 @@ static inline void _mi_free_block(mi_page_t* page, bool local, mi_block_t* block
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// and push it on the free list
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if (mi_likely(local)) {
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// owning thread can free a block directly
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if (mi_check_is_double_free(page, block)) return;
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mi_block_set_next(page, block, page->local_free);
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page->local_free = block;
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page->used--;
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@ -301,7 +310,7 @@ void mi_free(void* p) mi_attr_noexcept
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const mi_segment_t* const segment = _mi_ptr_segment(p);
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if (mi_unlikely(segment == NULL)) return; // checks for (p==NULL)
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#if (MI_DEBUG>0)
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#if (MI_DEBUG!=0)
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if (mi_unlikely(!mi_is_in_heap_region(p))) {
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_mi_warning_message("possibly trying to free a pointer that does not point to a valid heap region: 0x%p\n"
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"(this may still be a valid very large allocation (over 64MiB))\n", p);
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@ -310,7 +319,7 @@ void mi_free(void* p) mi_attr_noexcept
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}
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}
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#endif
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#if (MI_DEBUG>0 || MI_SECURE>=4)
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#if (MI_DEBUG!=0 || MI_SECURE>=4)
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if (mi_unlikely(_mi_ptr_cookie(segment) != segment->cookie)) {
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_mi_error_message("trying to free a pointer that does not point to a valid heap space: %p\n", p);
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return;
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@ -332,9 +341,7 @@ void mi_free(void* p) mi_attr_noexcept
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if (mi_likely(tid == segment->thread_id && page->flags.full_aligned == 0)) { // the thread id matches and it is not a full page, nor has aligned blocks
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// local, and not full or aligned
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mi_block_t* block = (mi_block_t*)p;
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#if MI_SECURE>=4
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if (mi_check_double_free(page,block)) return;
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#endif
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if (mi_check_is_double_free(page,block)) return;
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mi_block_set_next(page, block, page->local_free);
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page->local_free = block;
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page->used--;
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@ -15,14 +15,14 @@ const mi_page_t _mi_page_empty = {
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0, false, false, false, false, 0, 0,
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{ 0 }, false,
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NULL, // free
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#if MI_SECURE
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#if MI_ENCODE_FREELIST
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0,
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#endif
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0, // used
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NULL,
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ATOMIC_VAR_INIT(0), ATOMIC_VAR_INIT(0),
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0, NULL, NULL, NULL
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#if (MI_INTPTR_SIZE==8 && MI_SECURE>0) || (MI_INTPTR_SIZE==4 && MI_SECURE==0)
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#if (MI_INTPTR_SIZE==8 && defined(MI_ENCODE_FREELIST)) || (MI_INTPTR_SIZE==4 && !defined(MI_ENCODE_FREELIST))
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, { NULL } // padding
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#endif
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};
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@ -290,7 +290,9 @@ mi_attr_noreturn void _mi_fatal_error(const char* fmt, ...) {
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va_start(args, fmt);
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mi_vfprintf(NULL, "mimalloc: fatal: ", fmt, args);
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va_end(args);
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exit(99);
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#if (MI_SECURE>=0)
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abort();
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#endif
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}
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// --------------------------------------------------------
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@ -512,7 +512,7 @@ static mi_decl_noinline void mi_page_free_list_extend( mi_page_t* page, size_t e
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----------------------------------------------------------- */
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#define MI_MAX_EXTEND_SIZE (4*1024) // heuristic, one OS page seems to work well.
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#if MI_SECURE
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#if (MI_SECURE>0)
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#define MI_MIN_EXTEND (8*MI_SECURE) // extend at least by this many
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#else
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#define MI_MIN_EXTEND (1)
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@ -579,7 +579,7 @@ static void mi_page_init(mi_heap_t* heap, mi_page_t* page, size_t block_size, mi
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page->block_size = block_size;
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mi_assert_internal(page_size / block_size < (1L<<16));
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page->reserved = (uint16_t)(page_size / block_size);
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#if MI_SECURE
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#ifdef MI_ENCODE_FREELIST
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page->cookie = _mi_heap_random(heap) | 1;
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#endif
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page->is_zero = page->is_zero_init;
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@ -592,7 +592,7 @@ static void mi_page_init(mi_heap_t* heap, mi_page_t* page, size_t block_size, mi
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mi_assert_internal(page->next == NULL);
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mi_assert_internal(page->prev == NULL);
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mi_assert_internal(!mi_page_has_aligned(page));
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#if MI_SECURE
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#if (MI_ENCODE_FREELIST)
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mi_assert_internal(page->cookie != 0);
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#endif
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mi_assert_expensive(mi_page_is_valid_init(page));
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@ -9,11 +9,16 @@
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static void double_free1();
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static void double_free2();
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static void corrupt_free();
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int main() {
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mi_version();
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// detect double frees and heap corruption
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//double_free1();
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//double_free2();
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//corrupt_free();
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void* p1 = malloc(78);
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void* p2 = malloc(24);
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free(p1);
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@ -36,9 +41,13 @@ int main() {
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return 0;
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}
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// The double free samples come ArcHeap [1] by Insu Yun (issue #161)
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// [1]: https://arxiv.org/pdf/1903.00503.pdf
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static void double_free1() {
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void* p[256];
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uintptr_t buf[256];
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//uintptr_t buf[256];
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p[0] = mi_malloc(622616);
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p[1] = mi_malloc(655362);
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@ -54,7 +63,7 @@ static void double_free1() {
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static void double_free2() {
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void* p[256];
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uintptr_t buf[256];
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//uintptr_t buf[256];
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// [INFO] Command buffer: 0x327b2000
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// [INFO] Input size: 182
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p[0] = malloc(712352);
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@ -69,3 +78,32 @@ static void double_free2() {
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// p[4]=0x433f1402000 (size=917504), p[1]=0x433f14c2000 (size=786432)
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fprintf(stderr, "p1: %p-%p, p2: %p-%p\n", p[4], (uint8_t*)(p[4]) + 917504, p[1], (uint8_t*)(p[1]) + 786432);
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}
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// Try to corrupt the heap through buffer overflow
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#define N 256
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#define SZ 64
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static void corrupt_free() {
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void* p[N];
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// allocate
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for (int i = 0; i < N; i++) {
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p[i] = malloc(SZ);
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}
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// free some
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for (int i = 0; i < N; i += (N/10)) {
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free(p[i]);
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p[i] = NULL;
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}
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// try to corrupt the free list
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for (int i = 0; i < N; i++) {
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if (p[i] != NULL) {
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memset(p[i], 0, SZ+8);
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}
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}
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// allocate more.. trying to trigger an allocation from a corrupted entry
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// this may need many allocations to get there (if at all)
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for (int i = 0; i < 4096; i++) {
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malloc(SZ);
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}
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}
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