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randomize large allocation guard size

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This commit is contained in:
Daniel Micay 2018-08-26 04:42:01 -04:00
parent a13a45a17d
commit 14ca7d7c3f
1 changed files with 23 additions and 8 deletions
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31
malloc.c
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@ -456,6 +456,7 @@ static void slab_free(void *p) {
struct region_info { struct region_info {
void *p; void *p;
size_t size; size_t size;
size_t guard_size;
}; };
static const size_t initial_region_table_size = 256; static const size_t initial_region_table_size = 256;
@ -507,7 +508,7 @@ static int regions_grow(void) {
return 0; return 0;
} }
static int regions_insert(void *p, size_t size) { static int regions_insert(void *p, size_t size, size_t guard_size) {
if (regions_free * 4 < regions_total) { if (regions_free * 4 < regions_total) {
if (regions_grow()) { if (regions_grow()) {
return 1; return 1;
@ -523,6 +524,7 @@ static int regions_insert(void *p, size_t size) {
} }
regions[index].p = p; regions[index].p = p;
regions[index].size = size; regions[index].size = size;
regions[index].guard_size = guard_size;
regions_free--; regions_free--;
return 0; return 0;
} }
@ -670,20 +672,28 @@ static void enforce_init(void) {
} }
} }
static size_t get_guard_size(struct random_state *state, size_t size) {
return (get_random_u64_uniform(state, size / PAGE_SIZE / 8) + 1) * PAGE_SIZE;
}
static void *allocate(size_t size) { static void *allocate(size_t size) {
if (size <= max_slab_size_class) { if (size <= max_slab_size_class) {
return slab_allocate(size); return slab_allocate(size);
} }
void *p = allocate_pages(size, PAGE_SIZE, true); pthread_mutex_lock(&regions_lock);
size_t guard_size = get_guard_size(&regions_rng, size);
pthread_mutex_unlock(&regions_lock);
void *p = allocate_pages(size, guard_size, true);
if (p == NULL) { if (p == NULL) {
return NULL; return NULL;
} }
pthread_mutex_lock(&regions_lock); pthread_mutex_lock(&regions_lock);
if (regions_insert(p, size)) { if (regions_insert(p, size, guard_size)) {
pthread_mutex_unlock(&regions_lock); pthread_mutex_unlock(&regions_lock);
deallocate_pages(p, size, PAGE_SIZE); deallocate_pages(p, size, guard_size);
return NULL; return NULL;
} }
pthread_mutex_unlock(&regions_lock); pthread_mutex_unlock(&regions_lock);
@ -703,10 +713,11 @@ static void deallocate(void *p) {
fatal_error("invalid free"); fatal_error("invalid free");
} }
size_t size = region->size; size_t size = region->size;
size_t guard_size = region->guard_size;
regions_delete(region); regions_delete(region);
pthread_mutex_unlock(&regions_lock); pthread_mutex_unlock(&regions_lock);
deallocate_pages(p, size, PAGE_SIZE); deallocate_pages(p, size, guard_size);
} }
EXPORT void *h_malloc(size_t size) { EXPORT void *h_malloc(size_t size) {
@ -786,15 +797,19 @@ static int alloc_aligned(void **memptr, size_t alignment, size_t size, size_t mi
return 0; return 0;
} }
void *p = allocate_pages_aligned(size, alignment, PAGE_SIZE); pthread_mutex_lock(&regions_lock);
size_t guard_size = get_guard_size(&regions_rng, size);
pthread_mutex_unlock(&regions_lock);
void *p = allocate_pages_aligned(size, alignment, guard_size);
if (p == NULL) { if (p == NULL) {
return ENOMEM; return ENOMEM;
} }
pthread_mutex_lock(&regions_lock); pthread_mutex_lock(&regions_lock);
if (regions_insert(p, size)) { if (regions_insert(p, size, guard_size)) {
pthread_mutex_unlock(&regions_lock); pthread_mutex_unlock(&regions_lock);
deallocate_pages(p, size, PAGE_SIZE); deallocate_pages(p, size, guard_size);
return ENOMEM; return ENOMEM;
} }
pthread_mutex_unlock(&regions_lock); pthread_mutex_unlock(&regions_lock);