linux-kernel - [PATCH v3] i2c: validate user data in compat ioctl

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Message-Id: <20211230224750.15380-1-paskripkin@gmail.com>
Date:   Fri, 31 Dec 2021 01:47:50 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     wsa@...nel.org, viro@...iv.linux.org.uk
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+e417648b303855b91d8a@...kaller.appspotmail.com
Subject: [PATCH v3] i2c: validate user data in compat ioctl

Wrong user data may cause warning in i2c_transfer(), ex: zero msgs.
Userspace should not be able to trigger warnings, so this patch adds
validation checks for user data in compact ioctl to prevent reported
warnings

Reported-and-tested-by: syzbot+e417648b303855b91d8a@...kaller.appspotmail.com
Fixes: 7d5cb45655f2 ("i2c compat ioctls: move to ->compat_ioctl()")
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---

Changes in v3
	- Add rdwr_arg.nmsgs == 0 check as Wolfram suggested

Changes in v2:
	- Fixed typos in commit message

---
 drivers/i2c/i2c-dev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index bce0e8bb7852..cf5d049342ea 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -535,6 +535,9 @@ static long compat_i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned lo
 				   sizeof(rdwr_arg)))
 			return -EFAULT;
 
+		if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
+			return -EINVAL;
+
 		if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
 			return -EINVAL;
 
-- 
2.34.1