ptp: Properly handle compat ioctls

BugLink: https://bugs.launchpad.net/bugs/2111953

[ Upstream commit 19ae40f572a9ce1ade9954990af709a03fd37010 ]

Pointer arguments passed to ioctls need to pass through compat_ptr() to
work correctly on s390; as explained in Documentation/driver-api/ioctl.rst.
Detect compat mode at runtime and call compat_ptr() for those commands
which do take pointer arguments.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/lkml/1ba5d3a4-7931-455b-a3ce-85a968a7cb10@app.fastmail.com/
Fixes: d94ba80ebb ("ptp: Added a brand new class driver for ptp clocks.")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://patch.msgid.link/20250125-posix-clock-compat_ioctl-v2-1-11c865c500eb@weissschuh.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>

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>
@@ -178,6 +179,9 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
 
 	tsevq = pccontext->private_clkdata;
 
+	if (in_compat_syscall() && cmd != PTP_ENABLE_PPS && cmd != PTP_ENABLE_PPS2)
+		arg = (unsigned long)compat_ptr(arg);
+
 	switch (cmd) {
 
 	case PTP_CLOCK_GETCAPS: