[PATCH 14/14] HID: i2c-hid: fix i2c_hid_get_raw_report count mismatches

[Benjamin Tissoires]

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@xxxxxxxxx>
---
 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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