Commit 7eb71e03 authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

libceph: fix double __remove_osd() problem 

It turns out it's possible to get __remove_osd() called twice on the
same OSD.  That doesn't sit well with rb_erase() - depending on the
shape of the tree we can get a NULL dereference, a soft lockup or
a random crash at some point in the future as we end up touching freed
memory.  One scenario that I was able to reproduce is as follows:

            <osd3 is idle, on the osd lru list>
<con reset - osd3>
con_fault_finish()
  osd_reset()
                              <osdmap - osd3 down>
                              ceph_osdc_handle_map()
                                <takes map_sem>
                                kick_requests()
                                  <takes request_mutex>
                                  reset_changed_osds()
                                    __reset_osd()
                                      __remove_osd()
                                  <releases request_mutex>
                                <releases map_sem>
    <takes map_sem>
    <takes request_mutex>
    __kick_osd_requests()
      __reset_osd()
        __remove_osd() <-- !!!

A case can be made that osd refcounting is imperfect and reworking it
would be a proper resolution, but for now Sage and I decided to fix
this by adding a safe guard around __remove_osd().

Fixes: http://tracker.ceph.com/issues/8087



Cc: Sage Weil <sage@redhat.com>
Cc: stable@vger.kernel.org # 3.9+: 7c6e6fc5: libceph: assert both regular and lingering lists in __remove_osd()
Cc: stable@vger.kernel.org # 3.9+: cc9f1f51: libceph: change from BUG to WARN for __remove_osd() asserts
Cc: stable@vger.kernel.org # 3.9+
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
Reviewed-by: default avatarSage Weil <sage@redhat.com>
Reviewed-by: default avatarAlex Elder <elder@linaro.org>
parent 7ad18afa

net/ceph/osd_client.c

+18 −8
Original line number Original line Diff line number Diff line
@@ -1048,15 +1048,25 @@ static void put_osd(struct ceph_osd *osd) 
 */

 */

static void __remove_osd(struct ceph_osd_client *osdc, struct ceph_osd *osd)

static void __remove_osd(struct ceph_osd_client *osdc, struct ceph_osd *osd)

{

{

	dout("__remove_osd %p\n", osd);

	dout("%s %p osd%d\n", __func__, osd, osd->o_osd);

	WARN_ON(!list_empty(&osd->o_requests));

	WARN_ON(!list_empty(&osd->o_requests));

	WARN_ON(!list_empty(&osd->o_linger_requests));

	WARN_ON(!list_empty(&osd->o_linger_requests));





	rb_erase(&osd->o_node, &osdc->osds);

	list_del_init(&osd->o_osd_lru);

	list_del_init(&osd->o_osd_lru);

	rb_erase(&osd->o_node, &osdc->osds);

	RB_CLEAR_NODE(&osd->o_node);

}



static void remove_osd(struct ceph_osd_client *osdc, struct ceph_osd *osd)

{

	dout("%s %p osd%d\n", __func__, osd, osd->o_osd);



	if (!RB_EMPTY_NODE(&osd->o_node)) {

		ceph_con_close(&osd->o_con);

		ceph_con_close(&osd->o_con);

		__remove_osd(osdc, osd);

		put_osd(osd);

		put_osd(osd);

	}

	}

}





static void remove_all_osds(struct ceph_osd_client *osdc)

static void remove_all_osds(struct ceph_osd_client *osdc)

{

{
@@ -1065,7 +1075,7 @@ static void remove_all_osds(struct ceph_osd_client *osdc) 
	while (!RB_EMPTY_ROOT(&osdc->osds)) {

	while (!RB_EMPTY_ROOT(&osdc->osds)) {

		struct ceph_osd *osd = rb_entry(rb_first(&osdc->osds),

		struct ceph_osd *osd = rb_entry(rb_first(&osdc->osds),

						struct ceph_osd, o_node);

						struct ceph_osd, o_node);

		__remove_osd(osdc, osd);

		remove_osd(osdc, osd);

	}

	}

	mutex_unlock(&osdc->request_mutex);

	mutex_unlock(&osdc->request_mutex);

}

}
@@ -1106,7 +1116,7 @@ static void remove_old_osds(struct ceph_osd_client *osdc) 
	list_for_each_entry_safe(osd, nosd, &osdc->osd_lru, o_osd_lru) {

	list_for_each_entry_safe(osd, nosd, &osdc->osd_lru, o_osd_lru) {

		if (time_before(jiffies, osd->lru_ttl))

		if (time_before(jiffies, osd->lru_ttl))

			break;

			break;

		__remove_osd(osdc, osd);

		remove_osd(osdc, osd);

	}

	}

	mutex_unlock(&osdc->request_mutex);

	mutex_unlock(&osdc->request_mutex);

}

}
@@ -1121,8 +1131,7 @@ static int __reset_osd(struct ceph_osd_client *osdc, struct ceph_osd *osd) 
	dout("__reset_osd %p osd%d\n", osd, osd->o_osd);

	dout("__reset_osd %p osd%d\n", osd, osd->o_osd);

	if (list_empty(&osd->o_requests) &&

	if (list_empty(&osd->o_requests) &&

	    list_empty(&osd->o_linger_requests)) {

	    list_empty(&osd->o_linger_requests)) {

		__remove_osd(osdc, osd);

		remove_osd(osdc, osd);



		return -ENODEV;

		return -ENODEV;

	}

	}
@@ -1926,6 +1935,7 @@ static void reset_changed_osds(struct ceph_osd_client *osdc) 
{

{

	struct rb_node *p, *n;

	struct rb_node *p, *n;





	dout("%s %p\n", __func__, osdc);

	for (p = rb_first(&osdc->osds); p; p = n) {

	for (p = rb_first(&osdc->osds); p; p = n) {

		struct ceph_osd *osd = rb_entry(p, struct ceph_osd, o_node);

		struct ceph_osd *osd = rb_entry(p, struct ceph_osd, o_node);

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