Inheritance is a security loophole!

The lack of a permissions check for creating a child table means that
in current sources, any user can inject data of his choosing into
another user's tables. Example:

User A:

regression=> create table foo (f1 text);
CREATE
regression=> insert into foo values ('good data');
INSERT 271570 1

User B:

regression=> create table foohack () inherits (foo);
CREATE
regression=> insert into foohack values ('you have been hacked!');
INSERT 271598 1

Now User A sees:

regression=> select * from foo;
f1
-----------------------
good data
you have been hacked!
(2 rows)

User A can only avoid this trap by being very careful to specify ONLY
in every query. If he *intends* to use foo as an inheritance tree
master, then that cure doesn't work either.

Just to add insult to injury, user A is now unable to drop table foo.
He'll also get permission failures from commands like "UPDATE foo ..."

I suppose a proper fix would involve adding a new permission type "can
make child tables", but I don't want to mess with that at the moment.
For 7.1, I propose that we only allow creation of child tables to the
owner of the parent table.

Comments?

regards, tom lane

PS: another interesting problem: create a temp table, then create a
non-temp table that inherits from it. Unhappiness ensues when you
end your session. Need to prohibit this combination, I think.