netdev - [PATCH net v2] ptp: Properly handle compat ioctls

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Message-Id: <20250125-posix-clock-compat_ioctl-v2-1-11c865c500eb@weissschuh.net>
Date: Sat, 25 Jan 2025 10:28:38 +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>, 
 Anna-Maria Behnsen <anna-maria@...utronix.de>, 
 Frederic Weisbecker <frederic@...nel.org>, 
 Thomas Gleixner <tglx@...utronix.de>, John Stultz <jstultz@...gle.com>, 
 Arnd Bergmann <arnd@...db.de>, John Stultz <john.stultz@...aro.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Cyrill Gorcunov <gorcunov@...il.com>, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH net v2] 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@...db.de>
Link: https://lore.kernel.org/lkml/1ba5d3a4-7931-455b-a3ce-85a968a7cb10@app.fastmail.com/
Fixes: d94ba80ebbea ("ptp: Added a brand new class driver for ptp clocks.")
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Changes in v2:
- Use in_compat_syscall()
- Discard changes outside drivers/ptp/, they are independent,
  unsuited for the net tree and will be submitted on their own
- Link to v1: https://lore.kernel.org/r/20250121-posix-clock-compat_ioctl-v1-1-c70d5433a825@weissschuh.net
---
 drivers/ptp/ptp_chardev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index ea96a14d72d141a4b255563b66bac8ed568b45e9..bf6468c56419c56c0737515d614b2267264816c2 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>
@@ -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) {

---
base-commit: b46c89c08f4146e7987fc355941a93b12e2c03ef
change-id: 20250103-posix-clock-compat_ioctl-96fbac549146

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