Avoid an UB of adding NULL + 0 by keeping an offset instead of advancing the pointer into a vector struct

1 files changed, 46 insertions, 0 deletions

diff --git a/tests/t_vector.c b/tests/t_vector.c
index 541a6da..6e048e1 100644
--- a/tests/t_vector.c
+++ b/tests/t_vector.c
@@ -112,6 +112,51 @@ static void case_insert_keeps_order(void) {
   free(vector.data);
 }
 
+/* The peer variant is reached with an empty vector on every first announce
+   for a torrent, and again whenever a swarm empties and refills, because
+   vector_fixup_peers drops the allocation and nulls the data pointer. */
+
+static void case_insert_peer_into_empty_vector(void) {
+  ot_vector vector = {NULL, 0, 0};
+  ot_peer6  low, high;
+  int       exactmatch;
+  ot_peer  *slot;
+
+  memset(low, 0x11, sizeof(low));
+  memset(high, 0x99, sizeof(high));
+
+  test_case("the first peer goes into a vector that has no allocation yet");
+  slot = vector_find_or_insert_peer(&vector, low, OT_PEER_SIZE6, &exactmatch);
+  CHECK(slot != NULL);
+  CHECK_INT(exactmatch, 0);
+  memcpy(slot, low, OT_PEER_SIZE6);
+  CHECK_INT(vector.size, 1);
+  CHECK_INT(vector.space, OT_VECTOR_MIN_MEMBERS);
+  CHECK_PTR(slot, vector.data);
+
+  test_case("a second peer keeps the order");
+  slot = vector_find_or_insert_peer(&vector, high, OT_PEER_SIZE6, &exactmatch);
+  CHECK(slot != NULL);
+  CHECK_INT(exactmatch, 0);
+  memcpy(slot, high, OT_PEER_SIZE6);
+  CHECK_INT(vector.size, 2);
+  CHECK_MEM((char *)vector.data, low, OT_PEER_COMPARE_SIZE6);
+  CHECK_MEM((char *)vector.data + OT_PEER_SIZE6, high, OT_PEER_COMPARE_SIZE6);
+
+  test_case("and emptying the vector hands the allocation back");
+  CHECK(vector_remove_peer(&vector, low, OT_PEER_SIZE6) != 0);
+  CHECK(vector_remove_peer(&vector, high, OT_PEER_SIZE6) != 0);
+  CHECK_INT(vector.size, 0);
+  CHECK_PTR(vector.data, NULL);
+
+  test_case("so the next peer starts from no allocation again");
+  slot = vector_find_or_insert_peer(&vector, low, OT_PEER_SIZE6, &exactmatch);
+  CHECK(slot != NULL);
+  CHECK_INT(vector.size, 1);
+
+  free(vector.data);
+}
+
 static void case_insert_finds_existing(void) {
   ot_vector           vector = {NULL, 0, 0};
   const unsigned char five[4] = {0, 0, 0, 5};
@@ -257,6 +302,7 @@ void test_vector(void) {
   case_search_past_the_end();
   case_search_empty();
   case_insert_keeps_order();
+  case_insert_peer_into_empty_vector();
   case_insert_finds_existing();
   case_insert_compare_prefix();
   case_redistribute_holds_every_peer();