CVE-2022-49607

/// Technical description

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

perf/core: Fix data race between perf_event_set_output() and perf_mmap_close()

Yang Jihing reported a race between perf_event_set_output() and

perf_mmap_close():

CPU1 CPU2

perf_mmap_close(e2)

if (atomic_dec_and_test(&e2->rb->mmap_count)) // 1 - > 0

detach_rest = true

ioctl(e1, IOC_SET_OUTPUT, e2)

perf_event_set_output(e1, e2)

...

list_for_each_entry_rcu(e, &e2->rb->event_list, rb_entry)

ring_buffer_attach(e, NULL);

// e1 isn't yet added and

// therefore not detached

ring_buffer_attach(e1, e2->rb)

list_add_rcu(&e1->rb_entry,

&e2->rb->event_list)

After this; e1 is attached to an unmapped rb and a subsequent

perf_mmap() will loop forever more:

again:

mutex_lock(&e->mmap_mutex);

if (event->rb) {

...

if (!atomic_inc_not_zero(&e->rb->mmap_count)) {

...

mutex_unlock(&e->mmap_mutex);

goto again;

}

}

The loop

/// 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