[systemd-devel] Any reason why /run and /dev/shm do not have MS_NOEXEC flags set?

[Hoyer, Marko (ADITG/SW2)]

Thx for the ideas. I'll bring them up in an internal discussion as well.

Best regards

Marko Hoyer
Software Group II (ADITG/SW2)

Tel. +49 5121 49 6948

-----Original Message-----
From: systemd-devel [mailto:systemd-devel-bounces at lists.freedesktop.org] On Behalf Of Topi Miettinen
Sent: Mittwoch, 1. Februar 2017 18:11
To: systemd-devel at lists.freedesktop.org
Subject: Re: [systemd-devel] Any reason why /run and /dev/shm do not have MS_NOEXEC flags set?

On 02/01/17 13:13, Hoyer, Marko (ADITG/SW2) wrote:
> Hi,
> 
> thanks to all for your fast feedback. I'll kick off an internal 
> discussion based on the facts you delivered to find out if our people 
> actually want what they want ;)

Filesystem W^X is a nice idea, but considering scripting or other (even
unintentional) Turing complete interpreters in a system, its not very strong protection. See also https://lwn.net/Articles/708196/

In my setup I have mounted /run with noexec, but /run/user/* still exec.
Then for each service you can enable systemd directive ProtectHome=true which makes /run/user inaccessible.

Likewise for /dev/shm, you can check if it is needed by each service at all and make it completely inaccessible if so, rather than making it globally noexec.

-Topi

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