ptp: Ensure info->enable callback is always set

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>

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index b932425ddc6a3789504164a69d1b8eba47da462c..35a5994bf64f6373c08269d63aaeac3f4ab31ff0 100644 (file)
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -217,6 +217,11 @@ static int ptp_getcycles64(struct ptp_clock_info *info, struct timespec64 *ts)
                return info->gettime64(info, ts);
 }
 
+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,
@@ -294,6 +299,9 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
                        ptp->info->getcrosscycles = ptp->info->getcrosststamp;
        }
 
+       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_run_worker(0, "ptp%d", ptp->index);