jiangyiwen
2014-Jul-23 02:29 UTC
[Ocfs2-devel] [PATCH]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: jiangyiwen <jiangyiwen at huawei.com>
---
fs/ocfs2/dlm/dlmmaster.c | 10 ----------
fs/ocfs2/dlm/dlmthread.c | 10 ++++++++++
2 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 3087a21..8266bc2 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -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) ||
diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
index 9db869d..ca93b84 100644
--- a/fs/ocfs2/dlm/dlmthread.c
+++ b/fs/ocfs2/dlm/dlmthread.c
@@ -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) {
-- 1.8.4.3