linux-kernel - [PATCH RESEND net] ptp: Ensure info->enable callback is always set

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Message-Id: <20250123-ptp-enable-v1-1-b015834d3a47@weissschuh.net>
Date: Thu, 23 Jan 2025 08:22:40 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Richard Cochran <richardcochran@...il.com>, 
 Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 John Stultz <john.stultz@...aro.org>, Arnd Bergmann <arnd@...db.de>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH RESEND net] 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@...r.kernel.org
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 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 b932425ddc6a3789504164a69d1b8eba47da462c..35a5994bf64f6373c08269d63aaeac3f4ab31ff0 100644
--- 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);

---
base-commit: c4b9570cfb63501638db720f3bee9f6dfd044b82
change-id: 20250122-ptp-enable-831339c62428

Best regards,
-- 
Thomas Weißschuh <linux@...ssschuh.net>