On Sat, Jul 03, 2021 at 12:59:28PM +0200, John Wood wrote:

Hi,

On Fri, Jul 02, 2021 at 05:08:09PM +0000, Alexander Lobakin wrote:

quoted

On the other hand, it leaves a potentional window for attackers to
perform brute force from xattr-incapable filesystems. So at the end
of the day I think that the current implementation (a strong
rejection of such filesystems) is way more secure than having
a fallback I proposed.

I've been thinking more about this: that the Brute LSM depends on xattr
support and I don't like this part. I want that brute force attacks can
be detected and mitigated on every system (with minimal dependencies).
So, now I am working in a solution without this drawback. I have some
ideas but I need to work on it.

I have been coding and testing a bit my ideas but:

Trying to track the applications faults info using kernel memory ends up
in an easy to abuse system (denied of service due to large amount of memory
in use) :(

So, I continue with the v8 idea: xattr to track application crashes info.

quoted

I'm planning to make a patch which will eliminate such weird rootfs
type selection and just always use more feature-rich tmpfs if it's
compiled in. So, as an alternative, you could add it to your series
as a preparatory change and just add a Kconfig dependency on
CONFIG_TMPFS && CONFIG_TMPFS_XATTR to CONFIG_SECURITY_FORK_BRUTE
without messing with any fallbacks at all.
What do you think?

Great. But I hope this patch will not be necessary for Brute LSM :)

My words are no longer valid ;)

Thanks,
John Wood