Hi, At Tue, 22 Mar 2016 22:47:16 -0500, Jim Nasby <jim.na...@bluetreble.com> wrote in <56f211c4.6010...@bluetreble.com> > On 3/22/16 10:35 PM, Kyotaro HORIGUCHI wrote: > >> Even if we maintained some interlock for a backend's login role > >> identity, > >> >I hardly think it would be practical to e.g. lock during transient SET > >> >ROLE or security-definer-function-call operations. So it's not like > >> >we > >> >can let the permissions system assume that a role OID being inquired > >> >about > >> >always matches a live entry in pg_authid. > > Even if blocking DROPs is not perfect for all cases, > > unconditionally allowing to DROP a role still doesn't seem proper > > behavior, especially for replication roles. And session logins > > seem to me to have enough reason to be treated differently than > > disguising as another role using SET ROLE or sec-definer. > > There's probably a way this could be handled, since DROP ROLE is > presumably a very uncommon operation. Perhaps something as simple as > keeping a single OID in shared memory for the role about to be > dropped. That would serialize role drops, but I doubt that matters.
The OID in shared memory has the same role with a tuple with the OID in pg_authid in this patch. So it seems need a lock or a retry mechanism, or we see a message something like this:p | DROP ROLE: Another role is concurrently being dropped. > > The attached patch blocks DROP ROLE for roles that own active > > sessions, and on the other hand prevents a session from being > > activated if the login role is concurrently dropped. > > I think this is fine for now, but... what happens if you drop a role > that's in use on a streaming replica? Does replay stall or do we just > ignore it? It behaves as the same to the ordinary backends. DROP ROLE fails for any active walsender's session(?) role, or a new walsender rejects login attempts by the role under being dropped. > There should probably be some doc changes to go with the patch too, > no? Yes, this is a PoC. I'll provide documentation if this is acceptable, and necessary. "20.4 Dropping Roles" would be appropriate? http://www.postgresql.org/docs/9.5/static/role-removal.html Treating a session as an object dependent on the role could be cleaner but may be too complex and fragile.. regards, -- Kyotaro Horiguchi NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers