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libceph: fix race between delayed_work() and ceph_monc_stop()

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The way the delayed work is handled in ceph_monc_stop() is prone to
races with mon_fault() and possibly also finish_hunting().  Both of
these can requeue the delayed work which wouldn't be canceled by any of
the following code in case that happens after cancel_delayed_work_sync()
runs -- __close_session() doesn't mess with the delayed work in order
to avoid interfering with the hunting interval logic.  This part was
missed in commit b5d91704f5 ("libceph: behave in mon_fault() if
cur_mon < 0") and use-after-free can still ensue on monc and objects
that hang off of it, with monc->auth and monc->monmap being
particularly susceptible to quickly being reused.

To fix this:

- clear monc->cur_mon and monc->hunting as part of closing the session
  in ceph_monc_stop()
- bail from delayed_work() if monc->cur_mon is cleared, similar to how
  it's done in mon_fault() and finish_hunting() (based on monc->hunting)
- call cancel_delayed_work_sync() after the session is closed

Cc: stable@vger.kernel.org
Link: https://tracker.ceph.com/issues/66857
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
This commit is contained in:
Ilya Dryomov 2024-07-08 22:37:29 +02:00
parent 256abd8e55
commit 69c7b2fe4c
1 changed files with 12 additions and 2 deletions
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14
net/ceph/mon_client.c
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@ -1085,13 +1085,19 @@ static void delayed_work(struct work_struct *work)
struct ceph_mon_client *monc =
container_of(work, struct ceph_mon_client, delayed_work.work);
dout("monc delayed_work\n");
mutex_lock(&monc->mutex);
dout("%s mon%d\n", __func__, monc->cur_mon);
if (monc->cur_mon < 0) {
goto out;
}
if (monc->hunting) {
dout("%s continuing hunt\n", __func__);
reopen_session(monc);
} else {
int is_auth = ceph_auth_is_authenticated(monc->auth);
dout("%s is_authed %d\n", __func__, is_auth);
if (ceph_con_keepalive_expired(&monc->con,
CEPH_MONC_PING_TIMEOUT)) {
dout("monc keepalive timeout\n");
@ -1116,6 +1122,8 @@ static void delayed_work(struct work_struct *work)
}
}
__schedule_delayed(monc);
out:
mutex_unlock(&monc->mutex);
}
@ -1232,13 +1240,15 @@ EXPORT_SYMBOL(ceph_monc_init);
void ceph_monc_stop(struct ceph_mon_client *monc)
{
dout("stop\n");
cancel_delayed_work_sync(&monc->delayed_work);
mutex_lock(&monc->mutex);
__close_session(monc);
monc->hunting = false;
monc->cur_mon = -1;
mutex_unlock(&monc->mutex);
cancel_delayed_work_sync(&monc->delayed_work);
/*
* flush msgr queue before we destroy ourselves to ensure that:
* - any work that references our embedded con is finished.