hashtable: add bounds check in hashtableNext iterator

Prevent iteration beyond hashtable bounds by checking if iterator
is already at the end before proceeding with the main iteration loop.
This adds defensive bounds checking for table index and bucket index.

Signed-off-by: Uri Yagelnik <uriy@amazon.com>

Author: Uri Yagelnik

src/hashtable.c

@@ -148,6 +148,8 @@ void hashtableSetResizePolicy(hashtableResizePolicy policy) {
 #define ENTRIES_PER_BUCKET 7
 #define BUCKET_BITS_TYPE uint8_t
 #define BITS_NEEDED_TO_STORE_POS_WITHIN_BUCKET 3
+/* Iterator table value indicating iteration is complete */
+#define HASHTABLE_ITER_END_TABLE 2
 
 /* Selecting the number of buckets.
  *
@@ -2025,6 +2027,12 @@ void hashtableReleaseIterator(hashtableIterator *iterator) {
  * Returns false if there are no more entries. */
 bool hashtableNext(hashtableIterator *iterator, void **elemptr) {
     iter *iter = iteratorFromOpaque(iterator);
+
+    assert(iter->table <= HASHTABLE_ITER_END_TABLE);
+    if (iter->table == HASHTABLE_ITER_END_TABLE) {
+        return false;
+    }
+
     while (1) {
         if (iter->index == -1 && iter->table == 0) {
             /* It's the first call to next. */
@@ -2102,6 +2110,7 @@ bool hashtableNext(hashtableIterator *iterator, void **elemptr) {
         }
         return true;
     }
+    iter->table = HASHTABLE_ITER_END_TABLE;
     return false;
 }