ocfs2/dlm: serialize migration MLE cleanup on failure

A migration MLE has a base reference for the mastering answer and an
in-use reference held by dlm_migrate_lockres(). The finishing assertion
consumes the base reference, but migration failure drops it again
without checking whether the assertion already consumed it.

The target queues its migration worker before it acknowledges the
ALL_DONE packet, so its finishing assertion can be handled while the
sender still waits for the status. If the connection fails before the
status arrives, dlm_send_one_lockres() returns an error for a migration
that the target has already completed:

  Old-master sender                  Finishing assertion
  -----------------                  -------------------
  publish MLE; take in-use reference
  send ALL_DONE; wait for status
                                     take lookup reference
                                     unlink MLE
                                     put lookup and base references
  send returns a connection error
  put base reference again; free MLE
  put in-use reference; access freed MLE

dlm_assert_master_handler() holds dlm->spinlock from the MLE lookup to
the final puts, and it takes dlm->master_lock around the unlink and the
puts. Decide under the same locks: if the MLE is already unhashed, the
assertion consumed the base reference, so drop only the sender's in-use
reference. Otherwise unlink it before consuming the base reference so a
later assertion no longer finds it.

An assertion that got there first has also made the target the owner
and cleared DLM_LOCK_RES_MIGRATING. Treating the attempt as failed at
that point would leave the lockres owned by the target while this node
still holds the other nodes' locks and refmap bits, so it could neither
be purged nor migrated again. Finish our side as a completed migration
does instead: drop those locks under res->spinlock if the target still
owns the lockres, and recalculate its usage.

Use the same cleanup for the pre-send failure, the send failure and the
target-death failure paths. The sender's in-use reference keeps the MLE
alive until its final put outside the nested locks. Successful
migration retains its existing in-use-only put.

A target that has died cannot assert after the sender has seen its
death. The o2net node-down callback runs before the DLM one; it
disconnects the node and flushes the workqueue that runs the message
handlers, so an assertion already received has been handled by the time
the DLM removes the node from the domain map. A node that leaves the
domain cleanly sends its exit message only after its assertions have
been answered.

Two windows of the hand-over itself are left as they are: the handler
switches the owner and the sender drops the other nodes' locks moments
later, and an assertion from a live target that arrives after the
sender has given up still meets the owner check in the handler. Waiting
for the target before giving up would only stretch the first window
into the time in which recovery of the target can observe it.

KASAN report, only the relevant frames are kept:

BUG: KASAN: slab-use-after-free in dlm_put_mle_inuse+0xce/0xe0
Read of size 8 at addr ffff8881190e3c20 by task umount/593

Call Trace:
 <TASK>
 dlm_put_mle_inuse+0xce/0xe0
 dlm_migrate_lockres+0x16af/0x20d0
 dlm_empty_lockres+0x60a/0xbd0
 dlm_unregister_domain+0x53b/0x11d0
 o2cb_cluster_disconnect+0xa5/0x110
 ocfs2_cluster_disconnect+0x73/0xc0
 ocfs2_dlm_shutdown+0x311/0x440
 ocfs2_dismount_volume+0x696/0x940
 generic_shutdown_super+0x15f/0x490
 kill_block_super+0x40/0xa0
 deactivate_locked_super+0xae/0x120
 deactivate_super+0xa2/0xc0
 cleanup_mnt+0x217/0x450
 task_work_run+0x144/0x230
 </TASK>

Allocated by task 593:
 kmem_cache_alloc_noprof+0x20b/0x5c0
 dlm_migrate_lockres+0x20e/0x20d0
 dlm_empty_lockres+0x60a/0xbd0
 dlm_unregister_domain+0x53b/0x11d0
 o2cb_cluster_disconnect+0xa5/0x110
 ocfs2_cluster_disconnect+0x73/0xc0
 ocfs2_dlm_shutdown+0x311/0x440
 ocfs2_dismount_volume+0x696/0x940

Freed by task 593:
 kmem_cache_free+0x242/0x580
 __dlm_put_mle+0x4b2/0x660
 dlm_migrate_lockres+0x1690/0x20d0
 dlm_empty_lockres+0x60a/0xbd0
 dlm_unregister_domain+0x53b/0x11d0
 o2cb_cluster_disconnect+0xa5/0x110
 ocfs2_cluster_disconnect+0x73/0xc0
 ocfs2_dlm_shutdown+0x311/0x440

The buggy address belongs to the object at ffff8881190e3c00
 which belongs to the cache o2dlm_mle of size 480
The buggy address is located 32 bytes inside of
 freed 480-byte region [ffff8881190e3c00, ffff8881190e3de0)

Link: https://lore.kernel.org/pm-ocfs2-objects-candidate-0038-v9-659f247ea980d5f3fbeb@gmail.com
Fixes: 6714d8e86bf4 ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem")
Signed-off-by: Cen Zhang <zzzccc427@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Assisted-by: LLM
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Heming Zhao <heming.zhao@suse.com>
Cc: Jia-Ju Bai <baijiaju1990@gmail.com>
Cc: <jjzuming@gmail.com>
Cc: <stable@vger.kernel.org>

0 files changed, 0 insertions, 0 deletions