linux-kernel - [PATCH 14/14] HID: i2c-hid: fix i2c_hid_get_raw

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Date:	Tue,  4 Dec 2012 16:27:55 +0100
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Jean Delvare <khali@...ux-fr.org>, linux-input@...r.kernel.org,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 14/14] HID: i2c-hid: fix i2c_hid_get_raw_report count mismatches

The previous memcpy implementation relied on the size advertized by the
device. There were no guarantees that buf was big enough.

Some gymnastic is also required with the +2/-2 to take into account
the first 2 bytes where the total length is supplied by the device.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...il.com>
---
 drivers/hid/i2c-hid/i2c-hid.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index 62988f1..de3566f 100644
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -503,13 +503,14 @@ static int i2c_hid_get_raw_report(struct hid_device *hid,
 {
 	struct i2c_client *client = hid->driver_data;
 	struct i2c_hid *ihid = i2c_get_clientdata(client);
+	size_t rcount;
 	int ret;
 
 	if (report_type == HID_OUTPUT_REPORT)
 		return -EINVAL;
 
-	if (count > ihid->bufsize)
-		count = ihid->bufsize;
+	if (count > ihid->bufsize - 2)
+		count = ihid->bufsize - 2;
 
 	ret = i2c_hid_get_report(client,
 			report_type == HID_FEATURE_REPORT ? 0x03 : 0x01,
@@ -518,7 +519,13 @@ static int i2c_hid_get_raw_report(struct hid_device *hid,
 	if (ret < 0)
 		return ret;
 
-	count = ihid->inbuf[0] | (ihid->inbuf[1] << 8);
+	rcount = ihid->inbuf[0] | (ihid->inbuf[1] << 8);
+
+	if (!rcount)
+		return 0;
+
+	if (count > rcount - 2)
+		count = rcount - 2;
 
 	memcpy(buf, ihid->inbuf + 2, count);
 
-- 
1.8.0.1

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