Re: [PATCH 1/2] host/rootfs: remove /proc/kcore bind mounts

Alyssa Ross
2025-12-16T12:48:22Z

[-- Attachment #1: Type: text/plain, Size: 2709 bytes --]

Alyssa Ross <hi@alyssa.is> writes:

> Demi Marie Obenour <demiobenour@gmail.com> writes:
>
>> On 12/15/25 07:27, Alyssa Ross wrote:
>>> Neither of these services run as root any more, so they don't have
>>> access to /proc/kcore any more regardless. (Also we don't have
>>> /proc/kcore on aarch64 so this previously errored there.)
>>>
>>> Fixes: 62590b8 ("host/rootfs: Sandbox crosvm")
>>> Fixes: ec47d36 ("host/rootfs: Sandbox Cloud Hypervisor")
>>> Signed-off-by: Alyssa Ross <hi@alyssa.is>
>>> ---
>>> .../service/vm-services/template/data/service/vhost-user-gpu/run | 1 -
>>> host/rootfs/image/usr/bin/run-vmm | 1 -
>>> 2 files changed, 2 deletions(-)
>>>
>>> diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run
>>> index b1f9bac..e063a82 100755
>>> --- a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run
>>> +++ b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run
>>> @@ -40,7 +40,6 @@ bwrap
>>> --tmpfs /proc/irq
>>> --remount-ro /proc/irq
>>> --ro-bind /dev/null /proc/timer_list
>>> - --ro-bind /dev/null /proc/kcore
>>> --ro-bind /dev/null /proc/kallsyms
>>> --ro-bind /dev/null /proc/sysrq-trigger
>>> --
>>> diff --git a/host/rootfs/image/usr/bin/run-vmm b/host/rootfs/image/usr/bin/run-vmm
>>> index 0640239..e30b14c 100755
>>> --- a/host/rootfs/image/usr/bin/run-vmm
>>> +++ b/host/rootfs/image/usr/bin/run-vmm
>>> @@ -113,7 +113,6 @@ bwrap
>>> --tmpfs /proc/irq
>>> --remount-ro /proc/irq
>>> --ro-bind /dev/null /proc/timer_list
>>> - --ro-bind /dev/null /proc/kcore
>>> --ro-bind /dev/null /proc/kallsyms
>>> --ro-bind /dev/null /proc/sysrq-trigger
>>> --
>>>
>>> base-commit: 6ceeb9b236cc50d2bba90068533ca1b7ff229c8b
>>
>> /proc/sysrq-trigger and /proc/timer_list can also be dropped,
>> as they are not accessible to unprivileged users.
>
> And what about the others? I see systemd just makes them all read-only
> — is that only to protect against root? Do we still need to hide
> /proc/sys, /proc/scsi, /proc/acpi, /proc/fs, and /proc/irq? The only
> entry I see that's writable by non-root in any of those on my NixOS
> system is /proc/sys/kernel/ns_last_pid, which doesn't look very harmful…

I'm just going to drop the /proc/scsi bind mount as well for now to fix
aarch64, but if you still think it's necessary we can instead do the
kernel config change.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 227 bytes --]