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Sachin authored
Problem:- If we try to run this query with -WITH_ASAN=ON compiled server CREATE TABLE t1 (i INT); SET debug_dbug="+d,test_completely_invisible,test_invisible_index"; CREATE TABLE t2 LIKE t1; This will generate a stack buffer overflow error. ==8922==ERROR: AddressSanitizer: stack-buffer-overflow on address #ADDR Analyze:- Error is generated on this line if (((*last)=new list_node(info, &end_of_list))) So info is our Key*, &end_of_list is global variable and last == #ADDR So last is suspicious variable. And last is the variable present in alter_info ->key_list. Now the question is how this key_list->last gets wrong/ different stack variable. In the backtrace, we can see that key_list is generated in mysql_create_table_like_table by calling mysql_preapre_alter_table_function and dummy key_list is created by mysql_create_like_table. In the end on mysql_prepare_alter_table we call alter_info->key_list.swap(new_key_list); So there is two options either key_list is empty or not empty , IF it is not empty then there is no issues last ptr is replaced by thd->mem_root (allocated ptr) So problem arises when key_list is empty. It swaps the dummy last ptr by mysql_prepare_alter_table declared ptr. which is wrong. Solution:- We wont swap variable if list does not have any element.
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