CVE-2024-49976

/// Technical description

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

tracing/timerlat: Drop interface_lock in stop_kthread()

stop_kthread() is the offline callback for "trace/osnoise:online", since

commit 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing

of kthread in stop_kthread()"), the following ABBA deadlock scenario is

introduced:

T1 | T2 [BP] | T3 [AP]

osnoise_hotplug_workfn() | work_for_cpu_fn() | cpuhp_thread_fun()

| _cpu_down() | osnoise_cpu_die()

mutex_lock(&interface_lock) | | stop_kthread()

| cpus_write_lock() | mutex_lock(&interface_lock)

cpus_read_lock() | cpuhp_kick_ap() |

As the interface_lock here in just for protecting the "kthread" field of

the osn_var, use xchg() instead to fix this issue. Also use

for_each_online_cpu() back in stop_per_cpu_kthreads() as it can take

cp

/// 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