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ocfs2: avoid access invalid address when read o2dlm debug messages

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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: Yiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yiwen Jiang
2015-09-04 15:44:37 -07:00
committed by Linus Torvalds
parent 743b5f1434
commit f57a22ddec
2 changed files with 21 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
fs/ocfs2/dlm/dlmthread.c
View File

@@ -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) {