Re: Misplaced superuser check in pg_log_backend_memory_contexts()

On Sun, Jun 6, 2021 at 12:23 PM Michael Paquier <michael@paquier.xyz> wrote:
>
> Hi all,
>
> While reading the code of pg_log_backend_memory_contexts(), I have
> been surprised to see that the code would attempt to look at a PROC
> entry based on the given input PID *before* checking if the function
> has been called by a superuser.  This does not strike me as a good
> idea as this allows any users to call this function and to take
> ProcArrayLock in shared mode, freely.
>
> It seems to me that we had better check for a superuser at the
> beginning of the function, like in the attached.

pg_signal_backend still locks ProcArrayLock in shared mode first and then
checks for the superuser permissions. Of course, it does that for the
roleId i.e. superuser_arg(proc->roleId), but there's also superuser() check.

With Regards,
Bharath Rupireddy.