ptp: Properly handle compat ioctls

JIRA: https://issues.redhat.com/browse/RHEL-84646

commit 19ae40f
Author: Thomas Weißschuh <linux@weissschuh.net>
Date:   Sat Jan 25 10:28:38 2025 +0100

    ptp: Properly handle compat ioctls

    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: d94ba80 ("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: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

Author: CKI Backport Bot

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>
@@ -176,6 +177,9 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
 	struct timespec64 ts;
 	int enable, err = 0;
 
+	if (in_compat_syscall() && cmd != PTP_ENABLE_PPS && cmd != PTP_ENABLE_PPS2)
+		arg = (unsigned long)compat_ptr(arg);
+
 	tsevq = pccontext->private_clkdata;
 
 	switch (cmd) {