CVE-2022-50177

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

rcutorture: Fix ksoftirqd boosting timing and iteration

The RCU priority boosting can fail in two situations:

1) If (nr_cpus= > maxcpus=), which means if the total number of CPUs

is higher than those brought online at boot, then torture_onoff() may

later bring up CPUs that weren't online on boot. Now since rcutorture

initialization only boosts the ksoftirqds of the CPUs that have been

set online on boot, the CPUs later set online by torture_onoff won't

benefit from the boost, making RCU priority boosting fail.

2) The ksoftirqd kthreads are boosted after the creation of

rcu_torture_boost() kthreads, which opens a window large enough for these

rcu_torture_boost() kthreads to wait (despite running at FIFO priority)

for ksoftirqds that are still running at SCHED_NORMAL priority.

The issues can trigger for example with:

./kvm.sh --configs TREE01 --kconfig "CONFIG_RCU_BOOST=y"

[ 34.968561] rcu-torture: !!!

[ 34

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References