Add integer overflow check to the malloc wrappers

Add a check that the combined size of the buffer to allocate and
alloc_info_t does not exceed the maximum integer value representable
by size_t.

Author: LDong-Arm

platform/source/mbed_alloc_wrappers.cpp

@@ -114,7 +114,10 @@ extern "C" void *malloc_wrapper(struct _reent *r, size_t size, void *caller)
 #endif
 #if MBED_HEAP_STATS_ENABLED
     malloc_stats_mutex->lock();
-    alloc_info_t *alloc_info = (alloc_info_t *)__real__malloc_r(r, size + sizeof(alloc_info_t));
+    alloc_info_t *alloc_info = NULL;
+    if (size <= SIZE_MAX - sizeof(alloc_info_t)) {
+        alloc_info = (alloc_info_t *)__real__malloc_r(r, size + sizeof(alloc_info_t));
+    }
     if (alloc_info != NULL) {
         alloc_info->size = size;
         alloc_info->signature = MBED_HEAP_STATS_SIGNATURE;
@@ -301,7 +304,10 @@ extern "C" void *malloc_wrapper(size_t size, void *caller)
 #endif
 #if MBED_HEAP_STATS_ENABLED
     malloc_stats_mutex->lock();
-    alloc_info_t *alloc_info = (alloc_info_t *)SUPER_MALLOC(size + sizeof(alloc_info_t));
+    alloc_info_t *alloc_info = NULL;
+    if (size <= SIZE_MAX - sizeof(alloc_info_t)) {
+        alloc_info = (alloc_info_t *)SUPER_MALLOC(size + sizeof(alloc_info_t));
+    }
     if (alloc_info != NULL) {
         alloc_info->size = size;
         alloc_info->signature = MBED_HEAP_STATS_SIGNATURE;