CVE-2024-44958

A flaw was found in the Linux kernel. An unbalanced decrement and increment of the sched_smt_present counter can occur during CPU deactivation if the cpuset_cpu_inactive() function fails. A local attacker could exploit this condition, leading to a kernel warning and potentially a denial of service (DoS) as the system becomes unstable or crashes.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, Simultaneous Multithreading (SMT) can be disabled. Disabling SMT may have a performance impact on the system.

To disable SMT at boot time, add nosmt to the kernel command line in your boot loader configuration. For example, in GRUB:

1. Edit /etc/default/grub and add nosmt to the GRUB_CMDLINE_LINUX variable.
2. Regenerate the GRUB configuration:
   • For BIOS-based systems: grub2-mkconfig -o /boot/grub2/grub.cfg
   • For UEFI-based systems: grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg (adjust path for your distribution)
3. Reboot the system.

Alternatively, SMT can be disabled at runtime by writing off to /sys/devices/system/cpu/smt/control. This change is not persistent across reboots. echo off > /sys/devices/system/cpu/smt/control A system reboot is required for the nosmt kernel parameter to take effect.