CONFIG_IO_STRICT_DEVMEM could be enabled

[Laurent Bonnaud]

Ubuntu could enable CONFIG_IO_STRICT_DEVMEM to restrict userspace access of active io-memory ranges.

This could impact kernel debugability. In that case, you may reboot with
iomem=relaxed on the kernel command line to override this setting.

This config option is recommended by the Kernel Self Protection Project[1] and a 2019 study performed by Capsule 8 shows that it is enabled in many other major distro kernels[2].

[1] https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings
[2] https://capsule8.com/blog/millions-of-binaries-later-a-look-into-linux-hardening-in-the-wild/

In Ubuntu impish:

$ grep CONFIG_IO_STRICT_DEVMEM /boot/config-*
/boot/config-5.13.0-27-generic:# CONFIG_IO_STRICT_DEVMEM is not set
/boot/config-5.13.0-27-lowlatency:# CONFIG_IO_STRICT_DEVMEM is not set
/boot/config-5.16.3-051603-generic:# CONFIG_IO_STRICT_DEVMEM is not set
/boot/config-5.16.3-051603-lowlatency:# CONFIG_IO_STRICT_DEVMEM is not set

In Debian 11:

$ grep CONFIG_IO_STRICT_DEVMEM /boot/config-*
/boot/config-5.10.0-10-amd64:CONFIG_IO_STRICT_DEVMEM=y
/boot/config-5.10.0-11-amd64:CONFIG_IO_STRICT_DEVMEM=y

In Debian sid:

$ grep CONFIG_IO_STRICT_DEVMEM /boot/config-*
/boot/config-5.15.0-3-amd64:CONFIG_IO_STRICT_DEVMEM=y
/boot/config-5.15.0-3-rt-amd64:CONFIG_IO_STRICT_DEVMEM=y

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Laurent Bonnaud (laurent-bonnaud)]

In Ubuntu noble:

$ grep CONFIG_IO_STRICT_DEVMEM /boot/config-*
/boot/config-6.8.0-22-generic:# CONFIG_IO_STRICT_DEVMEM is not set
/boot/config-6.8.0-7-lowlatency:# CONFIG_IO_STRICT_DEVMEM is not set