Android init inside privileged redroid container overwrites host kernel.modprobe, silently breaking host module autoloading

[cda2]

Is your feature request related to a problem? Please describe.

Yes. AOSP's init.rc runs write /proc/sys/kernel/modprobe \n on
early-init ("Android doesn't need kernel module autoloading"). That is fine
on real devices — but this sysctl is not namespaced, so inside a
privileged redroid container the write escapes to the host and silently
disables module autoloading system-wide. Anything that needs a
not-yet-loaded kernel module after the container starts will fail, with
misleading symptoms.

In my case: while a redroid container was running, the host's Wi-Fi (WPA2)
failed its 4-way handshake with nl80211: key addition failed, and
NetworkManager kept reporting a wrong password. Kernel tracing showed
mac80211's ieee80211_key_alloc() returning -ENOENT — the host kernel could
not autoload the ccm crypto module because /proc/sys/kernel/modprobe had
been emptied.

Reproduced with redroid:14.0.0_64only-latest; the line is present in
redroid's own fork (remote-android/platform_system_core, branch
redroid-14.0.0_r2, rootdir/init.rc:22). The latest redroid 16 is
affected as well: it builds from stock AOSP android-16.0.0_r2, whose
rootdir/init.rc:22 still contains the write, and none of the
redroid-patches/android-16.0.0_r2 patches touch it.

Describe the solution you'd like

Neutralize this write in redroid's build so a container never touches the
host's kernel.modprobe. I'd be happy to send a PR against
platform_system_core (or a patch in redroid-patches) if that's the
preferred route.

Describe alternatives you've considered

Host-side workarounds that I currently use:

• Preload modules that may be needed later (e.g. ccm, gcm in
  /etc/modules-load.d/)
• Restore the sysctl after container start:
  sysctl -w kernel.modprobe=/sbin/modprobe (I run this from a systemd
  timer)

These work, but every redroid user has to rediscover them the hard way —
documenting the caveat in redroid-doc would also help.

Additional context

This may sound like an unusual setup, but I'm writing it down for anyone who
runs into the same problem someday. I develop on an ASUS ROG Flow Z13
(Strix Halo) laptop running CachyOS. After a reboot, Wi-Fi that had always
worked suddenly became unusable — NetworkManager kept insisting my password
was wrong. I assumed the usual suspects ("Arch being Arch again", or "the
MediaTek chip acting up") and wrestled with the wireless stack for hours:
kernel, firmware, and supplicant changes made no difference. It was beyond
what I could solve on my own, so I went through a long network-debugging
session with Claude (Fable), and the trail led somewhere unexpected: the
privileged redroid container. Once I cleaned it up and rebooted, Wi-Fi came
back as if nothing had ever happened.

Environment: kernel 7.1.3 (CachyOS/Arch), Docker with --privileged,
redroid:14.0.0_64only-latest.