perform size checks on memcpy/memmove/memset

- memset is disabled for now as it causes hangs
- underlying functions were copied from isoalloc, licensed Apache-2.0
	- credit Chris Rohlf for memcpy/memset
	- credit David Carlier for memmove
- use the fast path as some programs crash otherwise

Signed-off-by: Tavi <[email protected]>

Author: SkewedZeppelin

Android.bp

@@ -28,6 +28,7 @@ common_cflags = [
     "-DN_ARENA=1",
     "-DCONFIG_STATS=true",
     "-DCONFIG_SELF_INIT=false",
+    "-DCONFIG_BLOCK_OPS_CHECK_SIZE=false",
 ]
 
 cc_defaults {

CREDITS

@@ -23,6 +23,12 @@ h_malloc.c open-addressed hash table (regions_grow, regions_insert, regions_find
     ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
     OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
+h_malloc.c block operations (h_memcpy_real, h_memmove_real, h_memset_real):
+
+    Copyright (C) 2022, 2023 struct <[email protected]>
+    Copyright (C) 2023 David Carlier <[email protected]>
+    Apache-2.0
+
 libdivide:
 
     Copyright (C) 2010 - 2019 ridiculous_fish, <[email protected]>

Makefile

@@ -89,6 +89,10 @@ ifeq (,$(filter $(CONFIG_SELF_INIT),true false))
     $(error CONFIG_SELF_INIT must be true or false)
 endif
 
+ifeq (,$(filter $(CONFIG_BLOCK_OPS_CHECK_SIZE),true false))
+    $(error CONFIG_BLOCK_OPS_CHECK_SIZE must be true or false)
+endif
+
 CPPFLAGS += \
     -DCONFIG_SEAL_METADATA=$(CONFIG_SEAL_METADATA) \
     -DZERO_ON_FREE=$(CONFIG_ZERO_ON_FREE) \
@@ -108,7 +112,8 @@ CPPFLAGS += \
     -DCONFIG_CLASS_REGION_SIZE=$(CONFIG_CLASS_REGION_SIZE) \
     -DN_ARENA=$(CONFIG_N_ARENA) \
     -DCONFIG_STATS=$(CONFIG_STATS) \
-    -DCONFIG_SELF_INIT=$(CONFIG_SELF_INIT)
+    -DCONFIG_SELF_INIT=$(CONFIG_SELF_INIT) \
+    -DCONFIG_BLOCK_OPS_CHECK_SIZE=$(CONFIG_BLOCK_OPS_CHECK_SIZE)
 
 $(OUT)/libhardened_malloc$(SUFFIX).so: $(OBJECTS) | $(OUT)
 	$(CC) $(CFLAGS) $(LDFLAGS) -shared $^ $(LDLIBS) -o $@

README.md

@@ -276,6 +276,10 @@ The following boolean configuration options are available:
   hardware, which may become drastically lower in the future. Whether or not
   this feature is enabled, the metadata is all contained within an isolated
   memory region with high entropy random guard regions around it.
+* `CONFIG_BLOCK_OPS_CHECK_SIZE`: `true` or `false` (default) to ensure length
+  parameter of the memcpy/memmove/memset block operations are within
+  approximate bounds to minimize buffer overflows. Note, memset override is
+  currently disabled due to improper behavior.
 
 The following integer configuration options are available:
 

config/default.mk

@@ -21,3 +21,4 @@ CONFIG_CLASS_REGION_SIZE := 34359738368 # 32GiB
 CONFIG_N_ARENA := 4
 CONFIG_STATS := false
 CONFIG_SELF_INIT := true
+CONFIG_BLOCK_OPS_CHECK_SIZE := false

config/light.mk

@@ -21,3 +21,4 @@ CONFIG_CLASS_REGION_SIZE := 34359738368 # 32GiB
 CONFIG_N_ARENA := 4
 CONFIG_STATS := false
 CONFIG_SELF_INIT := true
+CONFIG_BLOCK_OPS_CHECK_SIZE := false

h_malloc.c

@@ -528,7 +528,7 @@ static void set_canary(UNUSED const struct slab_metadata *metadata, UNUSED void
     }
 #endif
 
-    memcpy((char *)p + size - canary_size, &metadata->canary_value, canary_size);
+    h_memcpy_real((char *)p + size - canary_size, &metadata->canary_value, canary_size);
 #endif
 }
 
@@ -541,7 +541,7 @@ static void check_canary(UNUSED const struct slab_metadata *metadata, UNUSED con
 #endif
 
     u64 canary_value;
-    memcpy(&canary_value, (const char *)p + size - canary_size, canary_size);
+    h_memcpy_real(&canary_value, (const char *)p + size - canary_size, canary_size);
 
 #ifdef HAS_ARM_MTE
     if (unlikely(canary_value == 0)) {
@@ -831,7 +831,7 @@ static inline void deallocate_small(void *p, const size_t *expected_size) {
 #endif
 
         if (ZERO_ON_FREE && !skip_zero) {
-            memset(p, 0, size - canary_size);
+            h_memset_real(p, 0, size - canary_size);
         }
     }
 
@@ -1502,7 +1502,7 @@ EXPORT void *h_calloc(size_t nmemb, size_t size) {
     total_size = adjust_size_for_canary(total_size);
     void *p = alloc(total_size);
     if (!ZERO_ON_FREE && likely(p != NULL) && total_size && total_size <= max_slab_size_class) {
-        memset(p, 0, total_size - canary_size);
+        h_memset_real(p, 0, total_size - canary_size);
     }
 #ifdef HAS_ARM_MTE
     // use an assert instead of adding a conditional to memset() above (freed memory is always
@@ -1624,7 +1624,7 @@ EXPORT void *h_realloc(void *old, size_t size) {
                 mutex_unlock(&ra->lock);
 
                 if (memory_remap_fixed(old, old_size, new, size)) {
-                    memcpy(new, old, copy_size);
+                    h_memcpy_real(new, old, copy_size);
                     deallocate_pages(old, old_size, old_guard_size);
                 } else {
                     memory_unmap((char *)old - old_guard_size, old_guard_size);
@@ -1646,7 +1646,7 @@ EXPORT void *h_realloc(void *old, size_t size) {
     if (copy_size > 0 && copy_size <= max_slab_size_class) {
         copy_size -= canary_size;
     }
-    memcpy(new, old_orig, copy_size);
+    h_memcpy_real(new, old_orig, copy_size);
     if (old_size <= max_slab_size_class) {
         deallocate_small(old, NULL);
     } else {
@@ -1874,6 +1874,100 @@ EXPORT size_t h_malloc_object_size_fast(const void *p) {
     return SIZE_MAX;
 }
 
+inline void *h_memcpy_real(void *dst, const void *src, size_t len) {
+#if CONFIG_BLOCK_OPS_CHECK_SIZE
+    if(dst == src || len == 0) {
+        return dst;
+    }
+
+    char *p_dst = (char *)dst;
+    char const *p_src = (char const *)src;
+
+    while(len--) {
+        *p_dst++ = *p_src++;
+    }
+
+    return dst;
+#else
+    return memcpy(dst, src, len);
+#endif
+}
+
+inline void *h_memmove_real(void *dst, const void *src, size_t len) {
+#if CONFIG_BLOCK_OPS_CHECK_SIZE
+    if(dst == src || len == 0) {
+        return dst;
+    }
+
+    char *p_dst = (char *)dst;
+    char const *p_src = (char const *)src;
+
+    if(p_src < p_dst) {
+        p_dst += len;
+        p_src += len;
+        while(len--) {
+            *--p_dst = *--p_src;
+        }
+    } else {
+        dst = h_memcpy_real(dst, src, len);
+    }
+
+    return dst;
+#else
+    return memmove(dst, src, len);
+#endif
+}
+
+inline void *h_memset_real(void *dst, int value, size_t len) {
+#if CONFIG_BLOCK_OPS_CHECK_SIZE
+    if(len == 0) {
+        return dst;
+    }
+
+    char *p_dst = (char *)dst;
+
+    while(len--) {
+        *p_dst++ = value;
+    }
+
+    return dst;
+#else
+    return memset(dst, value, len);
+#endif
+}
+
+#if CONFIG_BLOCK_OPS_CHECK_SIZE
+EXPORT void *h_memcpy(void *dst, const void *src, size_t len) {
+    if (len > malloc_object_size_fast(src)) {
+        fatal_error("memcpy read overflow");
+    }
+    if (len > malloc_object_size_fast(dst)) {
+        fatal_error("memcpy buffer overflow");
+    }
+
+    return h_memcpy_real(dst, src, len);
+}
+
+EXPORT void *h_memmove(void *dst, const void *src, size_t len) {
+    if (len > malloc_object_size_fast(src)) {
+        fatal_error("memmove read overflow");
+    }
+    if (len > malloc_object_size_fast(dst)) {
+        fatal_error("memmove buffer overflow");
+    }
+
+    return h_memmove_real(dst, src, len);
+}
+
+EXPORT void *h_memset(void *dst, int value, size_t len) {
+    if (len > malloc_object_size_fast(dst)) {
+        fatal_error("memset buffer overflow");
+    }
+
+    return h_memset_real(dst, value, len);
+}
+#endif
+
 EXPORT int h_mallopt(UNUSED int param, UNUSED int value) {
 #ifdef __ANDROID__
     if (param == M_PURGE) {

include/h_malloc.h

@@ -15,6 +15,11 @@ extern "C" {
 #define h_realloc realloc
 #define h_aligned_alloc aligned_alloc
 #define h_free free
+#if CONFIG_BLOCK_OPS_CHECK_SIZE
+#define h_memcpy memcpy
+#define h_memmove memmove
+//#define h_memset memset
+#endif
 
 #define h_posix_memalign posix_memalign
 
@@ -54,6 +59,14 @@ __attribute__((alloc_size(2))) void *h_realloc(void *ptr, size_t size);
 __attribute__((malloc)) __attribute__((alloc_size(2))) __attribute__((alloc_align(1)))
 void *h_aligned_alloc(size_t alignment, size_t size);
 void h_free(void *ptr);
+void *h_memcpy_real(void *dst, const void *src, size_t len);
+void *h_memmove_real(void *dst, const void *src, size_t len);
+void *h_memset_real(void *dst, int value, size_t len);
+#if CONFIG_BLOCK_OPS_CHECK_SIZE
+void *h_memcpy(void *dst, const void *src, size_t len);
+void *h_memmove(void *dst, const void *src, size_t len);
+void *h_memset(void *dst, int value, size_t len);
+#endif
 
 // POSIX
 int h_posix_memalign(void **memptr, size_t alignment, size_t size);

test/.gitignore

@@ -41,4 +41,15 @@ overflow_small_8_byte
 uninitialized_read_large
 uninitialized_read_small
 realloc_init
+memcpy_buffer_overflow
+memcpy_read_overflow
+memcpy_valid_same
+memcpy_valid_mismatched
+memmove_buffer_overflow
+memmove_read_overflow
+memmove_valid_same
+memmove_valid_mismatched
+memset_buffer_overflow
+memset_valid_same
+memset_valid_mismatched
 __pycache__/

test/Makefile

@@ -67,7 +67,18 @@ EXECUTABLES := \
     invalid_malloc_object_size_small \
     invalid_malloc_object_size_small_quarantine \
     impossibly_large_malloc \
-    realloc_init
+    realloc_init \
+    memcpy_buffer_overflow \
+    memcpy_read_overflow \
+    memcpy_valid_same \
+    memcpy_valid_mismatched \
+    memmove_buffer_overflow \
+    memmove_read_overflow \
+    memmove_valid_same \
+    memmove_valid_mismatched \
+    memset_buffer_overflow \
+    memset_valid_same \
+    memset_valid_mismatched
 
 all: $(EXECUTABLES)