This is a note to let you know that I've just added the patch titled fs: dlm: fix race between test_bit() and queue_work() to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: fs-dlm-fix-race-between-test_bit-and-queue_work.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From eef6ec9bf390e836a6c4029f3620fe49528aa1fe Mon Sep 17 00:00:00 2001 From: Alexander Aring <aahringo@xxxxxxxxxx> Date: Mon, 15 Aug 2022 15:43:14 -0400 Subject: fs: dlm: fix race between test_bit() and queue_work() From: Alexander Aring <aahringo@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx Signed-off-by: Alexander Aring <aahringo@xxxxxxxxxx> Signed-off-by: David Teigland <teigland@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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); @@ -286,7 +286,9 @@ 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); Patches currently in stable-queue which might be from aahringo@xxxxxxxxxx are queue-4.19/fs-dlm-handle-ebusy-first-in-lock-arg-validation.patch queue-4.19/fs-dlm-fix-race-between-test_bit-and-queue_work.patch