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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Yi Zeng <yizeng@asrmicro.com>,
        Wolfram Sang <wsa@the-dreams.de>, stable@kernel.org
Subject: [PATCH 4.20 34/57] i2c: dev: prevent adapter retries and timeout being set as minus value
Date:   Tue, 15 Jan 2019 17:36:15 +0100
Message-Id: <20190115154912.649215053@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yi Zeng <yizeng@asrmicro.com>

commit 6ebec961d59bccf65d08b13fc1ad4e6272a89338 upstream.

If adapter->retries is set to a minus value from user space via ioctl,
it will make __i2c_transfer and __i2c_smbus_xfer skip the calling to
adapter->algo->master_xfer and adapter->algo->smbus_xfer that is
registered by the underlying bus drivers, and return value 0 to all the
callers. The bus driver will never be accessed anymore by all users,
besides, the users may still get successful return value without any
error or information log print out.

If adapter->timeout is set to minus value from user space via ioctl,
it will make the retrying loop in __i2c_transfer and __i2c_smbus_xfer
always break after the the first try, due to the time_after always
returns true.

Signed-off-by: Yi Zeng <yizeng@asrmicro.com>
[wsa: minor grammar updates to commit message]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/i2c/i2c-dev.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -470,9 +470,15 @@ static long i2cdev_ioctl(struct file *fi
 					  data_arg.data);
 	}
 	case I2C_RETRIES:
+		if (arg > INT_MAX)
+			return -EINVAL;
+
 		client->adapter->retries = arg;
 		break;
 	case I2C_TIMEOUT:
+		if (arg > INT_MAX)
+			return -EINVAL;
+
 		/* For historical reasons, user-space sets the timeout
 		 * value in units of 10 ms.
 		 */