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improve hardening for same-class realloc by calling memory_corruption_check_small #312

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improve hardening for same-class realloc by calling memory_corruption_check_small #312

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79 changes: 42 additions & 37 deletions h_malloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -800,6 +800,42 @@ static void enqueue_free_slab(struct size_class *c, struct slab_metadata *metada
c->free_slabs_tail = substitute;
}

static inline void memory_corruption_check_small(const void *p, const char *unaligned_msg, const char *unused_slot_msg,
const char *quarantine_msg) {
struct slab_size_class_info size_class_info = slab_size_class(p);
size_t class = size_class_info.class;
struct size_class *c = &ro.size_class_metadata[size_class_info.arena][class];
size_t size = c->size;
bool is_zero_size = class == 0;
size_t slab_size = c->slab_size;

mutex_lock(&c->lock);

const struct slab_metadata *metadata = get_metadata(c, p);
void *slab = get_slab(c, slab_size, metadata);
size_t slot = libdivide_u32_do((const char *)p - (const char *)slab, &c->size_divisor);

if (unlikely(slot_pointer(size, slab, slot) != p)) {
fatal_error(unaligned_msg);
}

if (unlikely(!is_used_slot(metadata, slot))) {
fatal_error(unused_slot_msg);
}

if (likely(!is_zero_size)) {
check_canary(metadata, p, size);
}

#if SLAB_QUARANTINE
if (unlikely(is_quarantine_slot(metadata, slot))) {
fatal_error(quarantine_msg);
}
#endif

mutex_unlock(&c->lock);
}

// preserves errno
static inline void deallocate_small(void *p, const size_t *expected_size) {
struct slab_size_class_info size_class_info = slab_size_class(p);
Expand Down Expand Up @@ -1558,10 +1594,13 @@ EXPORT void *h_realloc(void *old, size_t size) {
bool old_in_slab_region = old < get_slab_region_end() && old >= ro.slab_region_start;
if (old_in_slab_region) {
old_size = slab_usable_size(old);
thread_unseal_metadata();
if (size <= max_slab_size_class && get_size_info(size).size == old_size) {
memory_corruption_check_small(old, "invalid unaligned h_realloc",
"invalid h_realloc (unused)", "invalid h_realloc (quarantine)");
thread_seal_metadata();
return old_orig;
}
thread_unseal_metadata();
} else {
enforce_init();
thread_unseal_metadata();
Expand Down Expand Up @@ -1755,41 +1794,6 @@ EXPORT void h_free_sized(void *p, size_t expected_size) {
thread_seal_metadata();
}

static inline void memory_corruption_check_small(const void *p) {
struct slab_size_class_info size_class_info = slab_size_class(p);
size_t class = size_class_info.class;
struct size_class *c = &ro.size_class_metadata[size_class_info.arena][class];
size_t size = c->size;
bool is_zero_size = class == 0;
size_t slab_size = c->slab_size;

mutex_lock(&c->lock);

const struct slab_metadata *metadata = get_metadata(c, p);
void *slab = get_slab(c, slab_size, metadata);
size_t slot = libdivide_u32_do((const char *)p - (const char *)slab, &c->size_divisor);

if (unlikely(slot_pointer(size, slab, slot) != p)) {
fatal_error("invalid unaligned malloc_usable_size");
}

if (unlikely(!is_used_slot(metadata, slot))) {
fatal_error("invalid malloc_usable_size");
}

if (likely(!is_zero_size)) {
check_canary(metadata, p, size);
}

#if SLAB_QUARANTINE
if (unlikely(is_quarantine_slot(metadata, slot))) {
fatal_error("invalid malloc_usable_size (quarantine)");
}
#endif

mutex_unlock(&c->lock);
}

EXPORT size_t h_malloc_usable_size(H_MALLOC_USABLE_SIZE_CONST void *arg) {
if (arg == NULL) {
return 0;
Expand All @@ -1799,7 +1803,8 @@ EXPORT size_t h_malloc_usable_size(H_MALLOC_USABLE_SIZE_CONST void *arg) {

if (p < get_slab_region_end() && p >= ro.slab_region_start) {
thread_unseal_metadata();
memory_corruption_check_small(p);
memory_corruption_check_small(p, "invalid unaligned malloc_usable_size",
"invalid malloc_usable_size (unused)", "invalid malloc_usable_size (quarantine)");
thread_seal_metadata();

size_t size = slab_usable_size(p);
Expand Down
2 changes: 1 addition & 1 deletion test/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ EXECUTABLES := \
string_overflow \
delete_type_size_mismatch \
unaligned_malloc_usable_size_small \
invalid_malloc_usable_size_small \
invalid_malloc_usable_size_small_unused \
invalid_malloc_usable_size_small_quarantine \
malloc_object_size \
malloc_object_size_offset \
Expand Down
0 test/invalid_malloc_usable_size_small.c → ...invalid_malloc_usable_size_small_unused.c
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File renamed without changes.
6 changes: 3 additions & 3 deletions test/test_smc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -105,12 +105,12 @@ def test_invalid_malloc_usable_size_small_quarantine(self):
self.assertEqual(stderr.decode(
"utf-8"), "fatal allocator error: invalid malloc_usable_size (quarantine)\n")

def test_invalid_malloc_usable_size_small(self):
def test_invalid_malloc_usable_size_small_unused(self):
_stdout, stderr, returncode = self.run_test(
"invalid_malloc_usable_size_small")
"invalid_malloc_usable_size_small_unused")
self.assertEqual(returncode, -6)
self.assertEqual(stderr.decode(
"utf-8"), "fatal allocator error: invalid malloc_usable_size\n")
"utf-8"), "fatal allocator error: invalid malloc_usable_size (unused)\n")

def test_read_after_free_large(self):
_stdout, _stderr, returncode = self.run_test("read_after_free_large")
Expand Down