From 91a0e1edb80a3cdeaa7b8810b65cc7abf6b85af8 Mon Sep 17 00:00:00 2001
From: Stephen Douthit <stephend@adiengineering.com>
Date: Mon, 7 Aug 2017 17:11:00 -0400
Subject: i2c: ismt: Return EMSGSIZE for block reads with bogus length

commit ba201c4f5ebe13d7819081756378777d8153f23e upstream.

Compare the number of bytes actually seen on the wire to the byte
count field returned by the slave device.

Previously we just overwrote the byte count returned by the slave
with the real byte count and let the caller figure out if the
message was sane.

Signed-off-by: Stephen Douthit <stephend@adiengineering.com>
Tested-by: Dan Priamo <danp@adiengineering.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c
index 8075a93..8477292 100644
--- a/drivers/i2c/busses/i2c-ismt.c
+++ b/drivers/i2c/busses/i2c-ismt.c
@@ -341,8 +341,10 @@ static int ismt_process_desc(const struct ismt_desc *desc,
 			break;
 		case I2C_SMBUS_BLOCK_DATA:
 		case I2C_SMBUS_I2C_BLOCK_DATA:
+			if (desc->rxbytes != dma_buffer[0] + 1)
+				return -EMSGSIZE;
+
 			memcpy(data->block, dma_buffer, desc->rxbytes);
-			data->block[0] = desc->rxbytes - 1;
 			break;
 		}
 		return 0;
-- 
cgit v0.10.2