Commit f57a22dd authored by Yiwen Jiang's avatar Yiwen Jiang Committed by Linus Torvalds
Browse files

ocfs2: avoid access invalid address when read o2dlm debug messages 



The following case will lead to a lockres is freed but is still in use.

cat /sys/kernel/debug/o2dlm/locking_state	dlm_thread
lockres_seq_start
    -> lock dlm->track_lock
    -> get resA
                                                resA->refs decrease to 0,
                                                call dlm_lockres_release,
                                                and wait for "cat" unlock.
Although resA->refs is already set to 0,
increase resA->refs, and then unlock
                                                lock dlm->track_lock
                                                    -> list_del_init()
                                                    -> unlock
                                                    -> free resA

In such a race case, invalid address access may occurs.  So we should
delete list res->tracking before resA->refs decrease to 0.

Signed-off-by: default avatarYiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: default avatarJoseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: default avatarMark Fasheh <mfasheh@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 743b5f14

fs/ocfs2/dlm/dlmmaster.c

+11 −11
Original line number Diff line number Diff line
@@ -498,16 +498,6 @@ static void dlm_lockres_release(struct kref *kref) 
	mlog(0, "destroying lockres %.*s\n", res->lockname.len,

	     res->lockname.name);



	spin_lock(&dlm->track_lock);

	if (!list_empty(&res->tracking))

		list_del_init(&res->tracking);

	else {

		mlog(ML_ERROR, "Resource %.*s not on the Tracking list\n",

		     res->lockname.len, res->lockname.name);

		dlm_print_one_lock_resource(res);

	}

	spin_unlock(&dlm->track_lock);



	atomic_dec(&dlm->res_cur_count);



	if (!hlist_unhashed(&res->hash_node) ||
@@ -795,8 +785,18 @@ lookup: 
		dlm_lockres_grab_inflight_ref(dlm, tmpres);



		spin_unlock(&tmpres->spinlock);

		if (res)

		if (res) {

			spin_lock(&dlm->track_lock);

			if (!list_empty(&res->tracking))

				list_del_init(&res->tracking);

			else

				mlog(ML_ERROR, "Resource %.*s not "

						"on the Tracking list\n",

						res->lockname.len,

						res->lockname.name);

			spin_unlock(&dlm->track_lock);

			dlm_lockres_put(res);

		}

		res = tmpres;

		goto leave;

	}

fs/ocfs2/dlm/dlmthread.c

+10 −0
Original line number Diff line number Diff line
@@ -211,6 +211,16 @@ static void dlm_purge_lockres(struct dlm_ctxt *dlm, 


	__dlm_unhash_lockres(dlm, res);



	spin_lock(&dlm->track_lock);

	if (!list_empty(&res->tracking))

		list_del_init(&res->tracking);

	else {

		mlog(ML_ERROR, "Resource %.*s not on the Tracking list\n",

				res->lockname.len, res->lockname.name);

		__dlm_print_one_lock_resource(res);

	}

	spin_unlock(&dlm->track_lock);



	/* lockres is not in the hash now.  drop the flag and wake up

	 * any processes waiting in dlm_get_lock_resource. */

	if (!master) {

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