With the default kernel and thus with the build I have tested in
74ec94bfa2, we get an error during
modules_install:
make[2]: execvp: /nix/store/.../bin/bash: Argument list too long
I haven't noticed this build until I actually tried booting using this
kernel because make didn't fail here.
The reason this happens within Nix and probably didn't yet surface in
other distros is that programs only have a limited amount of memory
available for storing the environment and the arguments.
Environment variables however are quite common on Nix and thus we
stumble on problems like this way earlier - in this case Linux 4.8 - but
I have noticed this in 4.7-next as well already.
The fix is far from perfect and suffers performance overhead because we
now run grep for every *.mod file instead of passing all *.mod files
into one single invocation of grep.
But comparing the performance overhead (around 1s on my machine) with
the overall build time of the kernel I think the overhead really is
neglicible.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Previously, features.grsecurity wasn't actually set due to a bug in the
grsec builder. We now rely on the generic kernel builder to set features
from kernelPatches.
Fixed for all available 4.x series kernels.
From CVE-2016-5829:
Multiple heap-based buffer overflows in the hiddev_ioctl_usage function
in drivers/hid/usbhid/hiddev.c in the Linux kernel through 4.6.3 allow
local users to cause a denial of service or possibly have unspecified
other impact via a crafted (1) HIDIOCGUSAGES or (2) HIDIOCSUSAGES ioctl
call.
This patch replaces the old grsecurity kernels with a single NixOS
specific grsecurity kernel. This kernel is intended as a general
purpose kernel, tuned for casual desktop use.
Providing only a single kernel may seem like a regression compared to
offering a multitude of flavors. It is impossible, however, to
effectively test and support that many options. This is amplified by
the reality that very few seem to actually use grsecurity on NixOS,
meaning that bugs go unnoticed for long periods of time, simply because
those code paths end up never being exercised. More generally, it is
hopeless to anticipate imagined needs. It is better to start from a
solid foundation and possibly add more flavours on demand.
While the generic kernel is intended to cover a wide range of use cases,
it cannot cover everything. For some, the configuration will be either
too restrictive or too lenient. In those cases, the recommended
solution is to build a custom kernel --- this is *strongly* recommended
for security sensitive deployments.
Building a custom grsec kernel should be as simple as
```nix
linux_grsec_nixos.override {
extraConfig = ''
GRKERNSEC y
PAX y
# and so on ...
'';
}
```
The generic kernel should be usable both as a KVM guest and host. When
running as a host, the kernel assumes hardware virtualisation support.
Virtualisation systems other than KVM are *unsupported*: users of
non-KVM systems are better served by compiling a custom kernel.
Unlike previous Grsecurity kernels, this configuration disables `/proc`
restrictions in favor of `security.hideProcessInformation`.
Known incompatibilities:
- ZFS: can't load spl and zfs kernel modules; claims incompatibility
with KERNEXEC method `or` and RAP; changing to `bts` does not fix the
problem, which implies we'd have to disable RAP as well for ZFS to
work
- `kexec()`: likely incompatible with KERNEXEC (unverified)
- Xen: likely incompatible with KERNEXEC and UDEREF (unverified)
- Virtualbox: likely incompatible with UDEREF (unverified)
Also revert to using the grsecurity-scrape mirror; relying on upstream
just isn't viable. Lately, updates have been so frequent that a new
version is released before Hydra even gets around to building the
previous one.
From now on, only the testing branch of grsecurity will be supported.
Additionally, use only patches from upstream.
It's impossible to provide meaningful support for grsecurity stable.
First, because building and testing \(m \times n \times z) [1], packages
is infeasible. Second, because stable patches are only available from
upstream for-pay, making us reliant on third-parties for patches. In
addition to creating yet more work for the maintainers, using stable
patches provided by a third-party goes against the wishes of upstream.
nixpkgs provides the tools necessary to build grsecurity kernels for any
version the user chooses, however, provided they pay for, or otherwise
acquire, the patch themselves.
Eventually, we'll want to remove the now obsolete top-level attributes,
but leave them in for now to smoothe migration (they have been removed
from top-level/release.nix, though, because it makes no sense to have
them there).
[1]: where \(m\) is the number of grsecurity flavors, \(n\) is the
number of kernel versions, and z is the size of the `linuxPackages` set
