From: Stephen Douthit <stephend@adiengineering.com>
Date: Mon, 7 Aug 2017 17:11:00 -0400
Subject: [PATCH] i2c: ismt: Return EMSGSIZE for block reads with bogus length
References: bnc#1060662
Patch-mainline: v4.12.11
Git-commit: ba201c4f5ebe13d7819081756378777d8153f23e

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/i2c/busses/i2c-ismt.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c
index 9af2337eb17a..22ffcb73c185 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;
-- 
2.14.2