Re: Worth using personality(ADDR_NO_RANDOMIZE) for EXEC_BACKEND on linux?

On 8/5/21 11:29 PM, Andres Freund wrote:
> Hi,
>
> When testing EXEC_BACKEND on linux I see occasional test failures as long as I
> don't disable ASLR. There's a code comment to that effect:
>
> 	 * If testing EXEC_BACKEND on Linux, you should run this as root before
> 	 * starting the postmaster:
> 	 *
> 	 * echo 0 >/proc/sys/kernel/randomize_va_space
>
> but I don't like doing that on a system wide basis.
>
> Linux allows disabling ASLR on a per-process basis using
> personality(ADDR_NO_RANDOMIZE). There's a wrapper binary to do that as well,
> setarch --addr-no-randomize.
>
> I was wondering if we should have postmaster do personality(ADDR_NO_RANDOMIZE)
> for EXEC_BACKEND builds? It seems nicer to make it automatically work than
> have people remember that they need to call "setarch --addr-no-randomize make check".
>
> Not that it actually matters for EXEC_BACKEND, but theoretically doing
> personality(ADDR_NO_RANDOMIZE) in postmaster is a tad more secure than doing
> it via setarch, as in the personality() case postmaster's layout itself is
> still randomized...
>
>
> Or perhaps we should just add a comment mentioning setarch.
>

If we can set it conveniently then that seems worth doing.


(Thinks: do we have non-Windows buildfarm members doing EXEC_BACKEND?)


cheers


andrew


--
Andrew Dunstan
EDB: https://www.enterprisedb.com