[PATCH 5.10.y 5.15.y] ptp: Ensure info->enable callback is always set

[Abdelkareem Abdelsaamad <kareemem@amazon.com>]

From: Thomas Weißschuh <linux@weissschuh.net>

commit fd53aa40e65f518453115b6f56183b0c201db26b upstream.

The ioctl and sysfs handlers unconditionally call the ->enable callback.
Not all drivers implement that callback, leading to NULL dereferences.
Example of affected drivers: ptp_s390.c, ptp_vclock.c and ptp_mock.c.

Instead use a dummy callback if no better was specified by the driver.

Fixes: d94ba80ebbea ("ptp: Added a brand new class driver for ptp clocks.")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/20250123-ptp-enable-v1-1-b015834d3a47@weissschuh.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[Conflict due to
42704b26b0f1 ("ptp: Add cycles support for virtual clocks")
not in the tree]
Signed-off-by: Abdelkareem Abdelsaamad <kareemem@amazon.com>
---
 drivers/ptp/ptp_clock.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index 4d775cd8ee3c..c895e26b1f17 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -188,6 +188,11 @@ static void ptp_clock_release(struct device *dev)
 	kfree(ptp);
 }
 
+static int ptp_enable(struct ptp_clock_info *ptp, struct ptp_clock_request *request, int on)
+{
+	return -EOPNOTSUPP;
+}
+
 static void ptp_aux_kworker(struct kthread_work *work)
 {
 	struct ptp_clock *ptp = container_of(work, struct ptp_clock,
@@ -233,6 +238,9 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	mutex_init(&ptp->pincfg_mux);
 	init_waitqueue_head(&ptp->tsev_wq);
 
+	if (!ptp->info->enable)
+		ptp->info->enable = ptp_enable;
+
 	if (ptp->info->do_aux_work) {
 		kthread_init_delayed_work(&ptp->aux_work, ptp_aux_kworker);
 		ptp->kworker = kthread_create_worker(0, "ptp%d", ptp->index);
-- 
2.47.1