Pointer arguments passed to ioctls need to pass through compat_ptr() to
work correctly on s390; as explained in Documentation/driver-api/ioctl.rst.
Plumb the compat_ioctl callback through 'struct posix_clock_operations'
and handle the different ioctls cmds in the new ptp_compat_ioctl().

Using compat_ptr_ioctl is not possible.
For the commands PTP_ENABLE_PPS/PTP_ENABLE_PPS2 on s390
it would corrupt the argument 0x80000000, aka BIT(31) to zero.

Fixes: 0606f422b453 ("posix clocks: Introduce dynamic clocks")
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>
---
 drivers/ptp/ptp_chardev.c   | 18 ++++++++++++++++++
 drivers/ptp/ptp_clock.c     |  1 +
 drivers/ptp/ptp_private.h   |  7 +++++++
 include/linux/posix-clock.h |  3 +++
 kernel/time/posix-clock.c   |  4 ++--
 5 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index ea96a14d72d141a4b255563b66bac8ed568b45e9..704af620c1173c12ee26b3b6c7982693e3c4c21f 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -4,6 +4,7 @@
  *
  * Copyright (C) 2010 OMICRON electronics GmbH
  */
+#include <linux/compat.h>
 #include <linux/module.h>
 #include <linux/posix-clock.h>
 #include <linux/poll.h>
@@ -507,6 +508,23 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
 	return err;
 }
 
+#ifdef CONFIG_COMPAT
+long ptp_compat_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
+		      unsigned long arg)
+{
+	switch (cmd) {
+	case PTP_ENABLE_PPS:
+	case PTP_ENABLE_PPS2:
+		/* These take in scalar arg, do not convert */
+		break;
+	default:
+		arg = (unsigned long)compat_ptr(arg);
+	}
+
+	return ptp_ioctl(pccontext, cmd, arg);
+}
+#endif
+
 __poll_t ptp_poll(struct posix_clock_context *pccontext, struct file *fp,
 		  poll_table *wait)
 {
diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index 77a36e7bddd54e8f45eab317e687f033f57cc5bc..dec84b81cedfd13bcf8c97be6c3c27d73cd671f6 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -180,6 +180,7 @@ static struct posix_clock_operations ptp_clock_ops = {
 	.clock_getres	= ptp_clock_getres,
 	.clock_settime	= ptp_clock_settime,
 	.ioctl		= ptp_ioctl,
+	.compat_ioctl	= ptp_compat_ioctl,
 	.open		= ptp_open,
 	.release	= ptp_release,
 	.poll		= ptp_poll,
diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
index 18934e28469ee6e3bf9c9e6d1a1adb82808d88e6..13999a7af47a7b67ae8dc549351fbafef2ae402f 100644
--- a/drivers/ptp/ptp_private.h
+++ b/drivers/ptp/ptp_private.h
@@ -133,6 +133,13 @@ int ptp_set_pinfunc(struct ptp_clock *ptp, unsigned int pin,
 long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
 	       unsigned long arg);
 
+#ifdef CONFIG_COMPAT
+long ptp_compat_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
+		      unsigned long arg);
+#else
+#define ptp_compat_ioctl NULL
+#endif
+
 int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode);
 
 int ptp_release(struct posix_clock_context *pccontext);
diff --git a/include/linux/posix-clock.h b/include/linux/posix-clock.h
index ef8619f489203eeb369ae580fc4d4b2439c94ae9..8bdc7aec5f7979c42752a233077620818d15acdd 100644
--- a/include/linux/posix-clock.h
+++ b/include/linux/posix-clock.h
@@ -54,6 +54,9 @@ struct posix_clock_operations {
 	long (*ioctl)(struct posix_clock_context *pccontext, unsigned int cmd,
 		      unsigned long arg);
 
+	long (*compat_ioctl)(struct posix_clock_context *pccontext, unsigned int cmd,
+			     unsigned long arg);
+
 	int (*open)(struct posix_clock_context *pccontext, fmode_t f_mode);
 
 	__poll_t (*poll)(struct posix_clock_context *pccontext, struct file *file,
diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
index 1af0bb2cc45c0aab843f77eb156992de469c8fb9..63184d92ef139c3fb9254745619ebca120fecce6 100644
--- a/kernel/time/posix-clock.c
+++ b/kernel/time/posix-clock.c
@@ -101,8 +101,8 @@ static long posix_clock_compat_ioctl(struct file *fp,
 	if (!clk)
 		return -ENODEV;
 
-	if (clk->ops.ioctl)
-		err = clk->ops.ioctl(pccontext, cmd, arg);
+	if (clk->ops.compat_ioctl)
+		err = clk->ops.compat_ioctl(pccontext, cmd, arg);
 
 	put_posix_clock(clk);
 

---
base-commit: 0bc21e701a6ffacfdde7f04f87d664d82e8a13bf
change-id: 20250103-posix-clock-compat_ioctl-96fbac549146

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