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

mainline inclusion
from mainline-v5.19-rc7
commit 68e3c698
category: bugfix
bugzilla: 187299, https://gitee.com/src-openeuler/kernel/issues/I5ISXP


CVE: NA

--------------------------------

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 in perf_mmap_close() holds e2->mmap_mutex, while the attach
in perf_event_set_output() holds e1->mmap_mutex. As such there is no
serialization to avoid this race.

Change perf_event_set_output() to take both e1->mmap_mutex and
e2->mmap_mutex to alleviate that problem. Additionally, have the loop
in perf_mmap() detach the rb directly, this avoids having to wait for
the concurrent perf_mmap_close() to get around to doing it to make
progress.

Fixes: 9bb5d40c ("perf: Fix mmap() accounting hole")
Reported-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Yang Jihong <yangjihong1@huawei.com>
Link: https://lkml.kernel.org/r/YsQ3jm2GR38SW7uD@worktop.programming.kicks-ass.net


Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Reviewed-by: Kuohai Xu <xukuohai@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>