[PATCH 5.19 036/717] fs: dlm: fix race between test_bit() and queue_work()

Greg Kroah-Hartman
2022-10-22T07:41:57Z

From: Alexander Aring <aahringo@redhat.com>

commit eef6ec9bf390e836a6c4029f3620fe49528aa1fe upstream.

This patch fixes a race by using ls_cb_mutex around the bit
operations and conditional code blocks for LSFL_CB_DELAY.

The function dlm_callback_stop() expects to stop all callbacks and
flush all currently queued onces. The set_bit() is not enough because
there can still be queue_work() after the workqueue was flushed.
To avoid queue_work() after set_bit(), surround both by ls_cb_mutex.

Cc: stable@vger.kernel.org
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/dlm/ast.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/dlm/ast.c
+++ b/fs/dlm/ast.c
@@ -200,13 +200,13 @@ void dlm_add_cb(struct dlm_lkb *lkb, uin
if (!prev_seq) {
kref_get(&lkb->lkb_ref);

+ mutex_lock(&ls->ls_cb_mutex);
if (test_bit(LSFL_CB_DELAY, &ls->ls_flags)) {
- mutex_lock(&ls->ls_cb_mutex);
list_add(&lkb->lkb_cb_list, &ls->ls_cb_delay);
- mutex_unlock(&ls->ls_cb_mutex);
} else {
queue_work(ls->ls_callback_wq, &lkb->lkb_cb_work);
}
+ mutex_unlock(&ls->ls_cb_mutex);
}
out:
mutex_unlock(&lkb->lkb_cb_mutex);
@@ -288,7 +288,9 @@ void dlm_callback_stop(struct dlm_ls *ls

void dlm_callback_suspend(struct dlm_ls *ls)
{
+ mutex_lock(&ls->ls_cb_mutex);
set_bit(LSFL_CB_DELAY, &ls->ls_flags);
+ mutex_unlock(&ls->ls_cb_mutex);

if (ls->ls_callback_wq)
flush_workqueue(ls->ls_callback_wq);