linux-kernel - [PATCH] char: ppdev: check if ioctl argument is present and valid

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Message-Id: <20201008182713.2764-1-harshalchau04@gmail.com>
Date:   Thu,  8 Oct 2020 23:57:13 +0530
From:   Harshal Chaudhari <harshalchau04@...il.com>
To:     gregkh@...uxfoundation.org
Cc:     arnd@...db.de, sudipm.mukherjee@...il.com,
        linux-kernel@...r.kernel.org, harshalchau04@...il.com
Subject: [PATCH] char: ppdev: check if ioctl argument is present and valid

Checking the argument passed to the ioctl is valid
or not. if not then return -EINVAL.

Signed-off-by: Harshal Chaudhari <harshalchau04@...il.com>
---
 drivers/char/ppdev.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
index 38b46c7d1737..001392980202 100644
--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -354,7 +354,7 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	unsigned int minor = iminor(file_inode(file));
 	struct pp_struct *pp = file->private_data;
 	struct parport *port;
-	void __user *argp = (void __user *)arg;
+	void __user *argp = NULL;
 	struct ieee1284_info *info;
 	unsigned char reg;
 	unsigned char mask;
@@ -364,6 +364,16 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	struct timespec64 ts;
 	int ret;
 
+	if (_IOC_TYPE(cmd) != PP_IOCTL)
+		return -ENOTTY;
+
+	/* check if ioctl argument is present and valid */
+	if (_IOC_DIR(cmd) != _IOC_NONE) {
+		argp = (void __user *)arg;
+		if (!argp)
+			return -EINVAL;
+	}
+
 	/* First handle the cases that don't take arguments. */
 	switch (cmd) {
 	case PPCLAIM:
-- 
2.17.1