Re: Possible null pointer dereference in afterTriggerAddEvent()

Alexander Kuznetsov <kuznetsovam@altlinux.org>

From: Alexander Kuznetsov <kuznetsovam@altlinux.org>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: pgsql-hackers@lists.postgresql.org, nickel@altlinux.org, egori@altlinux.org
Date: 2024-09-24T14:50:59Z
Lists: pgsql-hackers
Hello,

is there anything else we can help with or discuss in order to apply this fix?

26.07.2024 12:16, Alexander Kuznetsov пишет:
> 25.07.2024 20:07, Alvaro Herrera wrote:
>> Maybe for sanity (and perhaps for Svace compliance) we could do it the
>> other way around, i.e. by testing events->tail for nullness instead of
>> events->head, then add the assertion:
>>
>>         if (events->tail == NULL)
>>         {
>>             Assert(events->head == NULL);
>>             events->head = chunk;
>>         }
>>         else
>>             events->tail->next = chunk;
>>
>> This way, it's not wholly redundant.
> Thanks for your response!
> I agree with the proposed changes and have updated the patch accordingly. Version 2 is attached.
>> That said, I'm not sure we actually *need* to change this.
> I understand and partly agree. But it appears that with these changes, the dereference of a null pointer is impossible even in builds where assertions are disabled. Previously, this issue could theoretically occur. Consequently, these changes slightly enhance overall security.
> 

-- 
Best regards,
Alexander Kuznetsov



Commits

  1. Turn 'if' condition around to avoid Svace complaint