Subject: REVOKE's CASCADE protection doesn't work with INHERITed table owners

From: Jacob Champion <[email-masked]>
Date: Wed, 24 Jun 2026 14:57:13 -0700

Hi all,

I'm pretty sure the following is unintended behavior. It looks
potentially related to [1] as well.

TL;DR: The protection in recursive_revoke() against broken GRANT
OPTION chains doesn't seem to work properly when the grantee also
holds the privileges of the grantor.

= Setup =

With the following (contrived, minimized from the actual) setup:

    -- Set up a role hierarchy (as superuser "jacob")
    CREATE ROLE admins;
    CREATE ROLE bob;
    GRANT admins TO bob;

    -- Create two tables with different ownership
    CREATE TABLE my_table(i int);
    CREATE TABLE admin_table(i int);
    ALTER TABLE admin_table OWNER TO admins;

    -- Create a grant option chain on both tables
    GRANT ALL ON TABLE my_table TO bob WITH GRANT OPTION;
    GRANT ALL ON TABLE admin_table TO bob WITH GRANT OPTION;

    SET ROLE bob;
    GRANT ALL ON TABLE my_table TO bob;
    GRANT ALL ON TABLE admin_table TO bob;
    RESET ROLE;

Now we have the following ACLs:

    =# SELECT relname, relowner::regrole, relacl FROM pg_class
        WHERE relname LIKE '%_table';
    -[ RECORD 1
]-------------------------------------------------------------------
    relname  | my_table
    relowner | jacob
    relacl   | {jacob=arwdDxtm/jacob,bob=a*r*w*d*D*x*t*m*/jacob,bob=arwdDxtm/bob}
    -[ RECORD 2
]-------------------------------------------------------------------
    relname  | admin_table
    relowner | admins
    relacl   | {admins=arwdDxtm/admins,bob=a*r*w*d*D*x*t*m*/admins,bob=arwdDxtm/bob}

= Bug =

With that grant option chain, we try to prevent REVOKE [RESTRICT]
invocations that would cause problems:

    =# REVOKE ALL ON TABLE my_table FROM bob;
    ERROR:  dependent privileges exist
    HINT:  Use CASCADE to revoke them too.

But this protection doesn't work for the admin_table...

    =# REVOKE ALL ON TABLE admin_table FROM bob;
    REVOKE

...resulting in an orphaned ACL.

    -[ RECORD 2
]----------------------------------------------------------------
    relname  | admin_table
    relowner | admins
    relacl   | {admins=arwdDxtm/admins,bob=arwdDxtm/bob}

Dump/restores of this situation result in complaints, since user "bob"
isn't able to recreate the grant.

I think the issue is in recursive_revoke()'s usage of aclmask(), which
in turn uses has_privs_of_role(). It doesn't seem like that's what was
wanted in this particular case... thoughts?

Thanks,
--Jacob

[1] https://postgr.es/m/CAM6Zo8wD7RtQNhbQHODc9DobiW+GpT=[email-masked]

---

From: Jacob Champion <[email-masked]>
Date: Thu, 25 Jun 2026 17:12:42 -0700

[moving to -hackers]

> holds the privileges of the grantor.

More accurately: "when an intermediate grantor in the chain only
indirectly holds the ability to grant."

> wanted in this particular case... thoughts?

I propose changing that to aclmask_direct(), as in the attached, and
backpatching all the way down.

To try to prove to myself that this works, I added tests to pin each
of the three cases that are treated differently by aclmask_direct():
1. the grantor has indirect ownership privileges
2. the grantor has indirect grant options via INHERIT
3. the grantor has indirect grant options via PUBLIC (which is already
disallowed in practice)

I also tried to expand the existing comment, both to point out the
pitfall and to explain why the short-circuit works. But I've rewritten
it at least a dozen times, so if anyone can tell me whether I've made
sense and/or used the terminology appropriately, I'd appreciate it.

> potentially related to [1] as well.

(To fix [1] I suspect we need to make a similar tweak to
check_circularity(), but I haven't looked into that yet.)

Thanks!
--Jacob

---

From: Ayush Tiwari <[email-masked]>
Date: Mon, 6 Jul 2026 16:33:03 +0530

Hi,

> 3. the grantor has indirect grant options via PUBLIC (which is already

Thanks, this looks right to me.  I traced recursive_revoke() and the
aclmask() -> aclmask_direct() switch makes sense to me, since a
grant is only ever attributed to a role that holds the option directly
(or the owner), it seems right that recursive_revoke() should judge
"still has it" the same way, rather than counting inherited/superuser
access?  The three new test cases line up with that too.

> sense and/or used the terminology appropriately, I'd appreciate it.

One tiny comment question: the phrase "granted by any role on the chain"
in the new comment reads a little oddly to me, would something like
"still holds the option directly via another grantor" be closer to what
the code checks?  Could just be me misreading it.

Apart from the above, patch LGTM.

> [1]
> https://postgr.es/m/CAM6Zo8wD7RtQNhbQHODc9DobiW+GpT=[email-masked]

On check_circularity() for [1]: I tried the same aclmask_direct() swap,
but since it runs on every GRANT ... WITH GRANT OPTION, which
pg_dump/restore replays, erroring there could make restore/pg_upgrade of
an existing cluster (one already holding the [1] self-grant) fail. Feels
like it may need a companion dump/restore change first.

Regards,
Ayush

---

From: Jacob Champion <[email-masked]>
Date: Wed, 8 Jul 2026 15:54:06 -0700

On Mon, Jul 6, 2026 at 4:03 AM Ayush Tiwari <[email-masked]> wrote:
> Thanks, this looks right to me.

Thanks for the review!

> the code checks?

The first sentence is still "The grantee might still have some grant
options via another grantor," and I don't think adding "direct" would
have helped me understand this any better the first time I read it.
I'm definitely up for more bikeshedding, though, because I don't
really like what I have...

> an existing cluster (one already holding the [1] self-grant) fail.

Well, I think the complaint in [1] is that dump/restore *already*
fails, no? Can you provide an example of a correct (or benignly
incorrect) dump that would start failing?

As an aside, I'm not sure if check_circularity() is correctly
preventing cycles independently of this issue, so that part may end up
spiraling a bit.

Thanks,
--Jacob

---

From: Ayush Tiwari <[email-masked]>
Date: Thu, 9 Jul 2026 20:18:19 +0530

Hi,

> really like what I have...

Fair. The part that tripped me up was actually the second sentence,
"granted by any role on the chain", since the code isn't checking whether
some role could grant them, but whether the grantee itself still holds
them directly via another grantor. Maybe something like "if the grantee
still holds a grant option directly through another grantor, that
privilege's chain is intact"? No strong opinion though.

> incorrect) dump that would start failing?

The already-failing case in [1] is the one where the membership has
been revoked (REVOKE member FROM owner), which leaves a true orphan.
But the self-grant gets created as soon as an inheriting member does
the redundant WITH GRANT OPTION self-grant, and if the membership is
still in place, that cluster dumps and restores fine today.

  CREATE ROLE owner_role;
  CREATE ROLE member_role LOGIN;
  GRANT owner_role TO member_role;          -- membership kept
  CREATE TABLE t (i int);
  ALTER TABLE t OWNER TO owner_role;
  GRANT SELECT ON t TO member_role WITH GRANT OPTION;
  SET ROLE member_role;
  GRANT SELECT ON t TO member_role WITH GRANT OPTION;   -- self-grant

  relacl = {owner_role=arwdDxtm/owner_role,
            member_role=r*/owner_role,
            member_role=r*/member_role}

pg_dump emits "SET SESSION AUTHORIZATION member_role; GRANT SELECT ON
t TO member_role WITH GRANT OPTION;". Restoring that into a fresh
cluster works today, but with the check_circularity() change it fails
with "grant options cannot be granted back to your own grantor".

So it's not that [1] is fine today; it's that the fix also breaks a
broader set of clusters that currently round-trip (membership still
present), including via pg_upgrade. That's why I think the
check_circularity() side needs a companion dump/restore change rather
than going in on its own.

> preventing cycles independently of this issue, so that part may end up

Agreed, I did not check that either.

Regards,
Ayush