From 61c1edf1e2e8bae673ab933f0e39af8477e1b52e Mon Sep 17 00:00:00 2001 From: jiangyiwen Date: Fri, 30 Jan 2015 13:11:19 +1100 Subject: [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 Cc: Joel Becker Cc: Mark Fasheh Signed-off-by: Andrew Morton (cherry picked from commit e87e805fe4a1cf38031ae0669e3a91c8a8251279) --- 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 fdf4b41d0609..7d4472ce3a8d 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 69aac6f088ad..2e5e6d5fffe8 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) { -- 2.50.1