From: "daniel.starke@siemens.com" daniel.starke@siemens.com
stable inclusion from stable-v5.10.103 commit 1f0641dd0b6c60093825337563e1c9abec41757c bugzilla: https://gitee.com/openeuler/kernel/issues/I56NE7
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 96b169f05cdcc844b400695184d77e42071d14f2 upstream.
The here fixed commit made the tty hangup asynchronous to avoid a circular locking warning. I could not reproduce this warning. Furthermore, due to the asynchronous hangup the function call now gets queued up while the underlying tty is being freed. Depending on the timing this results in a NULL pointer access in the global work queue scheduler. To be precise in process_one_work(). Therefore, the previous commit made the issue worse which it tried to fix.
This patch fixes this by falling back to the old behavior which uses a blocking tty hangup call before freeing up the associated tty.
Fixes: 7030082a7415 ("tty: n_gsm: avoid recursive locking with async port hangup") Cc: stable@vger.kernel.org Signed-off-by: Daniel Starke daniel.starke@siemens.com Link: https://lore.kernel.org/r/20220218073123.2121-4-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yu Liao liaoyu15@huawei.com Reviewed-by: Wei Li liwei391@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- drivers/tty/n_gsm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 8e062cc46641..6d3265397d30 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1719,7 +1719,12 @@ static void gsm_dlci_release(struct gsm_dlci *dlci) gsm_destroy_network(dlci); mutex_unlock(&dlci->mutex);
- tty_hangup(tty); + /* We cannot use tty_hangup() because in tty_kref_put() the tty + * driver assumes that the hangup queue is free and reuses it to + * queue release_one_tty() -> NULL pointer panic in + * process_one_work(). + */ + tty_vhangup(tty);
tty_port_tty_set(&dlci->port, NULL); tty_kref_put(tty);