linux-kernel - [PATCH 4.9 117/240] tty: fix return value for unsupported ioctls

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Message-Id: <20210520092112.595493899@linuxfoundation.org>
Date:   Thu, 20 May 2021 11:21:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 117/240] tty: fix return value for unsupported ioctls

From: Johan Hovold <johan@...nel.org>

[ Upstream commit 1b8b20868a6d64cfe8174a21b25b74367bdf0560 ]

Drivers should return -ENOTTY ("Inappropriate I/O control operation")
when an ioctl isn't supported, while -EINVAL is used for invalid
arguments.

Fix up the TIOCMGET, TIOCMSET and TIOCGICOUNT helpers which returned
-EINVAL when a tty driver did not implement the corresponding
operations.

Note that the TIOCMGET and TIOCMSET helpers predate git and do not get a
corresponding Fixes tag below.

Fixes: d281da7ff6f7 ("tty: Make tiocgicount a handler")
Signed-off-by: Johan Hovold <johan@...nel.org>
Link: https://lore.kernel.org/r/20210407095208.31838-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/tty_io.c       | 8 ++++----
 include/linux/tty_driver.h | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 7b4aca20cb29..e16a74b68cd0 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2791,14 +2791,14 @@ out:
  *	@p: pointer to result
  *
  *	Obtain the modem status bits from the tty driver if the feature
- *	is supported. Return -EINVAL if it is not available.
+ *	is supported. Return -ENOTTY if it is not available.
  *
  *	Locking: none (up to the driver)
  */
 
 static int tty_tiocmget(struct tty_struct *tty, int __user *p)
 {
-	int retval = -EINVAL;
+	int retval = -ENOTTY;
 
 	if (tty->ops->tiocmget) {
 		retval = tty->ops->tiocmget(tty);
@@ -2816,7 +2816,7 @@ static int tty_tiocmget(struct tty_struct *tty, int __user *p)
  *	@p: pointer to desired bits
  *
  *	Set the modem status bits from the tty driver if the feature
- *	is supported. Return -EINVAL if it is not available.
+ *	is supported. Return -ENOTTY if it is not available.
  *
  *	Locking: none (up to the driver)
  */
@@ -2828,7 +2828,7 @@ static int tty_tiocmset(struct tty_struct *tty, unsigned int cmd,
 	unsigned int set, clear, val;
 
 	if (tty->ops->tiocmset == NULL)
-		return -EINVAL;
+		return -ENOTTY;
 
 	retval = get_user(val, p);
 	if (retval)
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index b742b5e47cc2..ae63c962fa22 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -235,7 +235,7 @@
  *
  *	Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
  *	structure to complete. This method is optional and will only be called
- *	if provided (otherwise EINVAL will be returned).
+ *	if provided (otherwise ENOTTY will be returned).
  */
 
 #include <linux/export.h>
-- 
2.30.2