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ARM MTE: properly check the memory tag of small allocations for h_free/h_free_sized/h_free_aligned_sized during deallocation #368

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ARM MTE: properly check the memory tag of small allocations for h_free/h_free_sized/h_free_aligned_sized during deallocation #368

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2 changes: 1 addition & 1 deletion androidtest/memtag/memtag_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -139,7 +139,7 @@ void tag_distinctness() {
p[j]++;
}

allocations[i] = addr;
allocations[i] = (uptr) p;
}

// free some of allocations to allow their slots to be reused
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36 changes: 25 additions & 11 deletions h_malloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -801,7 +801,13 @@ static void enqueue_free_slab(struct size_class *c, struct slab_metadata *metada
}

// preserves errno
static inline void deallocate_small(void *p, const size_t *expected_size) {
static inline void deallocate_small(void *tagged_p, const size_t *expected_size) {
#ifdef HAS_ARM_MTE
u8 supplied_tag = get_pointer_tag(tagged_p);
#endif

void *p = untag_pointer(tagged_p);

struct slab_size_class_info size_class_info = slab_size_class(p);
size_t class = size_class_info.class;

Expand Down Expand Up @@ -830,6 +836,14 @@ static inline void deallocate_small(void *p, const size_t *expected_size) {
fatal_error("double free");
}

#ifdef HAS_ARM_MTE
if (likely51(is_memtag_enabled())) {
if (unlikely(supplied_tag != get_pointer_tag(__arm_mte_get_tag(p)))) {
fatal_error("invalid free (memory tag)");
}
}
#endif

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

Expand Down Expand Up @@ -1684,7 +1698,7 @@ EXPORT void *h_realloc(void *old, size_t size) {
}
memcpy(new, old_orig, copy_size);
if (old_in_slab_region) {
deallocate_small(old, NULL);
deallocate_small(old_orig, NULL);
} else {
deallocate_large(old, NULL);
}
Expand Down Expand Up @@ -1735,17 +1749,17 @@ EXPORT void h_free(void *p) {
return;
}

p = untag_pointer(p);
void *untagged_p = untag_pointer(p);

if (p < get_slab_region_end() && p >= ro.slab_region_start) {
if (untagged_p < get_slab_region_end() && untagged_p >= ro.slab_region_start) {
thread_unseal_metadata();
deallocate_small(p, NULL);
thread_seal_metadata();
return;
}

int saved_errno = errno;
deallocate_large(p, NULL);
deallocate_large(untagged_p, NULL);
errno = saved_errno;

thread_seal_metadata();
Expand All @@ -1760,11 +1774,11 @@ EXPORT void h_free_sized(void *p, size_t expected_size) {
return;
}

p = untag_pointer(p);
void *untagged_p = untag_pointer(p);

expected_size = adjust_size_for_canary(expected_size);

if (p < get_slab_region_end() && p >= ro.slab_region_start) {
if (untagged_p < get_slab_region_end() && untagged_p >= ro.slab_region_start) {
if (unlikely(expected_size > max_slab_size_class)) {
fatal_error("sized deallocation mismatch (small)");
}
Expand All @@ -1777,7 +1791,7 @@ EXPORT void h_free_sized(void *p, size_t expected_size) {
}

int saved_errno = errno;
deallocate_large(p, &expected_size);
deallocate_large(untagged_p, &expected_size);
errno = saved_errno;

thread_seal_metadata();
Expand All @@ -1788,11 +1802,11 @@ EXPORT void h_free_aligned_sized(void *p, size_t alignment, size_t expected_size
return;
}

p = untag_pointer(p);
void *untagged_p = untag_pointer(p);

expected_size = adjust_size_for_canary(expected_size);

if (p < get_slab_region_end() && p >= ro.slab_region_start) {
if (untagged_p < get_slab_region_end() && untagged_p >= ro.slab_region_start) {
if (unlikely((alignment - 1) & alignment || alignment > PAGE_SIZE)) {
fatal_error("invalid sized deallocation alignment (small)");
}
Expand All @@ -1814,7 +1828,7 @@ EXPORT void h_free_aligned_sized(void *p, size_t alignment, size_t expected_size
}

int saved_errno = errno;
deallocate_large(p, &expected_size);
deallocate_large(untagged_p, &expected_size);
errno = saved_errno;

thread_seal_metadata();
Expand Down