Re: Possible null pointer dereference in afterTriggerAddEvent()

From: Alexander Kuznetsov <kuznetsovam(at)altlinux(dot)org>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org, nickel(at)altlinux(dot)org, egori(at)altlinux(dot)org
Subject: Re: Possible null pointer dereference in afterTriggerAddEvent()
Date: 2024-07-26 09:16:00
Message-ID: 8ddb8e6a-e899-4218-870f-8b25da3a9f3f@altlinux.org
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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

Attachment Content-Type Size
v2-0001-Add-assertion-of-an-empty-list-in-afterTriggerAdd.patch text/x-patch 1.1 KB

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