On 25.10.2011 19:37, Jeff Davis wrote:
> On Mon, 2011-10-24 at 13:15 +0300, Heikki Linnakangas wrote:
>> Hmm, I don't think that's safe. After Oid wraparound, a range type oid
>> might get reused for some other range type, and the cache would return
>> stale values. Extremely unlikely to happen by accident, but could be
>> exploited by an attacker.
>
> Any ideas on how to remedy that? I don't have another plan for making it
> perform well. Plugging it into the cache invalidation mechanism seems
> like overkill, but I suppose that would solve the problem.
I think we should look at the array-functions for precedent. array_in et
al cache the information in fn_extra, so that when it's called
repeatedly in one statement for the same type, the information is only
looked up once. That's good enough, it covers repeated execution in a
single query, as well as COPY and comparison calls from index searches,
for example.
> Aren't there a few other cases like this floating around the code?
Not that I know of. That said, I wouldn't be too surprised if there was.
> I know the single-xid cache is potentially vulnerable to xid wraparound
> for the same reason.
True.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com