linux-kernel - [PATCH 3.2 008/101] USB: serial: ark3116: fix register-accessor error handling

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Message-ID: <lsq.1496331655.313319037@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:40:55 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Johan Hovold" <johan@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.2 008/101] USB: serial: ark3116: fix register-accessor
 error handling

3.2.89-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit 9fef37d7cf170522fb354d6d0ea6de09b9b16678 upstream.

The current implementation failed to detect short transfers, something
which could lead to bits of the uninitialised heap transfer buffer
leaking to user space.

Fixes: 149fc791a452 ("USB: ark3116: Setup some basic infrastructure for
new ark3116 driver.")
Fixes: f4c1e8d597d1 ("USB: ark3116: Make existing functions 16450-aware
and add close and release functions.")
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/serial/ark3116.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/drivers/usb/serial/ark3116.c
+++ b/drivers/usb/serial/ark3116.c
@@ -107,10 +107,17 @@ static int ark3116_read_reg(struct usb_s
 				 usb_rcvctrlpipe(serial->dev, 0),
 				 0xfe, 0xc0, 0, reg,
 				 buf, 1, ARK_TIMEOUT);
-	if (result < 0)
+	if (result < 1) {
+		dev_err(&serial->interface->dev,
+				"failed to read register %u: %d\n",
+				reg, result);
+		if (result >= 0)
+			result = -EIO;
+
 		return result;
-	else
-		return buf[0];
+	}
+
+	return buf[0];
 }
 
 static inline int calc_divisor(int bps)