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libceph: fix double __remove_osd() problem

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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+: 7c6e6fc53e: libceph: assert both regular and lingering lists in __remove_osd()
Cc: stable@vger.kernel.org # 3.9+: cc9f1f518c: libceph: change from BUG to WARN for __remove_osd() asserts
Cc: stable@vger.kernel.org # 3.9+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
This commit is contained in:
Ilya Dryomov 2015-02-17 19:37:15 +03:00
parent 7ad18afad0
commit 7eb71e0351
1 changed files with 18 additions and 8 deletions
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26
net/ceph/osd_client.c
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@ -1048,14 +1048,24 @@ static void put_osd(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_linger_requests));
rb_erase(&osd->o_node, &osdc->osds);
list_del_init(&osd->o_osd_lru);
ceph_con_close(&osd->o_con);
put_osd(osd);
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);
__remove_osd(osdc, osd);
put_osd(osd);
}
}
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)) {
struct ceph_osd *osd = rb_entry(rb_first(&osdc->osds),
struct ceph_osd, o_node);
__remove_osd(osdc, osd);
remove_osd(osdc, osd);
}
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) {
if (time_before(jiffies, osd->lru_ttl))
break;
__remove_osd(osdc, osd);
remove_osd(osdc, osd);
}
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);
if (list_empty(&osd->o_requests) &&
list_empty(&osd->o_linger_requests)) {
__remove_osd(osdc, osd);
remove_osd(osdc, osd);
return -ENODEV;
}
@ -1926,6 +1935,7 @@ static void reset_changed_osds(struct ceph_osd_client *osdc)
{
struct rb_node *p, *n;
dout("%s %p\n", __func__, osdc);
for (p = rb_first(&osdc->osds); p; p = n) {
struct ceph_osd *osd = rb_entry(p, struct ceph_osd, o_node);