CVE-2022-49090

/// Technical description

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

arch/arm64: Fix topology initialization for core scheduling

Arm64 systems rely on store_cpu_topology() to call update_siblings_masks()

to transfer the toplogy to the various cpu masks. This needs to be done

before the call to notify_cpu_starting() which tells the scheduler about

each cpu found, otherwise the core scheduling data structures are setup

in a way that does not match the actual topology.

With smt_mask not setup correctly we bail on `cpumask_weight(smt_mask) == 1`

for !leaders in:

notify_cpu_starting()

cpuhp_invoke_callback_range()

sched_cpu_starting()

sched_core_cpu_starting()

which leads to rq->core not being correctly set for !leader-rq's.

Without this change stress-ng (which enables core scheduling in its prctl

tests in newer versions -- i.e. with PR_SCHED_CORE support) causes a warning

and then a crash (trimmed for legibility):

[ 1853.805168] ------------[ cut here ]------------

[

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. 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.

/// References