MDEV-19838: followup to make happy following protocol implementations:

- mysqlnd from PHP < 7.3
- mysql-connector-python any version
- mysql-connector-java any version

Relaxed check about garbage at the end of the packet in case of no parameters.
Added check for array binding.
Fixed test according to the new paradigm (allow junk at the end of the packet)

sql/sql_prepare.cc

@@ -3271,10 +3271,19 @@ void mysqld_stmt_execute(THD *thd, char *packet_arg, uint packet_length)
 void mysqld_stmt_bulk_execute(THD *thd, char *packet_arg, uint packet_length)
 {
   uchar *packet= (uchar*)packet_arg; // GCC 4.0.1 workaround
+  DBUG_ENTER("mysqld_stmt_execute_bulk");
+
+  const uint packet_header_lenght= 4 + 2; //ID & 2 bytes of flags
+
+  if (packet_length < packet_header_lenght)
+  {
+    my_error(ER_MALFORMED_PACKET, MYF(0));
+    DBUG_VOID_RETURN;
+  }
+
   ulong stmt_id= uint4korr(packet);
   uint flags= (uint) uint2korr(packet + 4);
   uchar *packet_end= packet + packet_length;
-  DBUG_ENTER("mysqld_stmt_execute_bulk");
 
   if (!(thd->client_capabilities &
         MARIADB_CLIENT_STMT_BULK_OPERATIONS))
@@ -3282,16 +3291,18 @@ void mysqld_stmt_bulk_execute(THD *thd, char *packet_arg, uint packet_length)
     DBUG_PRINT("error",
                ("An attempt to execute bulk operation without support"));
     my_error(ER_UNSUPPORTED_PS, MYF(0));
+    DBUG_VOID_RETURN;
   }
   /* Check for implemented parameters */
   if (flags & (~STMT_BULK_FLAG_CLIENT_SEND_TYPES))
   {
     DBUG_PRINT("error", ("unsupported bulk execute flags %x", flags));
     my_error(ER_UNSUPPORTED_PS, MYF(0));
+    DBUG_VOID_RETURN;
   }
 
   /* stmt id and two bytes of flags */
-  packet+= 4 + 2;
+  packet+= packet_header_lenght;
   mysql_stmt_execute_common(thd, stmt_id, packet, packet_end, 0, TRUE,
                             (flags & STMT_BULK_FLAG_CLIENT_SEND_TYPES));
   DBUG_VOID_RETURN;
@@ -3368,9 +3379,11 @@ stmt_execute_packet_sanity_check(Prepared_statement *stmt,
   {
     /*
       If there is no parameters, this should be normally already end
-      of the packet. If it's not - then error
+      of the packet, but it is not a problem if something left (popular
+      mistake in protocol implementation) because we will not read anymore
+      from the buffer.
     */
-    return (packet_end > packet);
+    return false;
   }
   return false;
 }

tests/mysql_client_test.c

@@ -20032,8 +20032,11 @@ static void test_mdev19838()
       " VALUES "
       "(0x1111111111111111)", -1);
 
-    /* Expecting an error if parameters are sent */
-    DIE_UNLESS(rc != 0 || paramCount == 0);
+    /*
+      We allow junk at the end of the packet in case of
+      no parameters. So it will succeed.
+    */
+    DIE_UNLESS(rc == 0);
   }
 
   mysql_stmt_close(stmt);