From 50fc7b61959af4b95fafce7fe5dd565199e0b61a Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben.hutchings@codethink.co.uk>
Date: Tue, 19 Jun 2018 11:17:32 -0700
Subject: [PATCH] Input: elan_i2c_smbus - fix more potential stack buffer overflows
Git-commit: 50fc7b61959af4b95fafce7fe5dd565199e0b61a
Patch-mainline: v4.18-rc3
References: bsc#1051510

Commit 40f7090bb1b4 ("Input: elan_i2c_smbus - fix corrupted stack")
fixed most of the functions using i2c_smbus_read_block_data() to
allocate a buffer with the maximum block size.  However three
functions were left unchanged:

* In elan_smbus_initialize(), increase the buffer size in the same
  way.
* In elan_smbus_calibrate_result(), the buffer is provided by the
  caller (calibrate_store()), so introduce a bounce buffer.  Also
  name the result buffer size.
* In elan_smbus_get_report(), the buffer is provided by the caller
  but happens to be the right length.  Add a compile-time assertion
  to ensure this remains the case.

Cc: <stable@vger.kernel.org> # 3.19+
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/input/mouse/elan_i2c.h       |  2 ++
 drivers/input/mouse/elan_i2c_core.c  |  2 +-
 drivers/input/mouse/elan_i2c_smbus.c | 10 ++++++++--
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/input/mouse/elan_i2c.h b/drivers/input/mouse/elan_i2c.h
index 599544c1a91c..243e0fa6e3e3 100644
--- a/drivers/input/mouse/elan_i2c.h
+++ b/drivers/input/mouse/elan_i2c.h
@@ -27,6 +27,8 @@
 #define ETP_DISABLE_POWER	0x0001
 #define ETP_PRESSURE_OFFSET	25
 
+#define ETP_CALIBRATE_MAX_LEN	3
+
 /* IAP Firmware handling */
 #define ETP_PRODUCT_ID_FORMAT_STRING	"%d.0"
 #define ETP_FW_NAME		"elan_i2c_" ETP_PRODUCT_ID_FORMAT_STRING ".bin"
diff --git a/drivers/input/mouse/elan_i2c_core.c b/drivers/input/mouse/elan_i2c_core.c
index f69d21610166..1f9cd7d8b7ad 100644
--- a/drivers/input/mouse/elan_i2c_core.c
+++ b/drivers/input/mouse/elan_i2c_core.c
@@ -613,7 +613,7 @@ static ssize_t calibrate_store(struct device *dev,
 	int tries = 20;
 	int retval;
 	int error;
-	u8 val[3];
+	u8 val[ETP_CALIBRATE_MAX_LEN];
 
 	retval = mutex_lock_interruptible(&data->sysfs_mutex);
 	if (retval)
diff --git a/drivers/input/mouse/elan_i2c_smbus.c b/drivers/input/mouse/elan_i2c_smbus.c
index cfcb32559925..c060d270bc4d 100644
--- a/drivers/input/mouse/elan_i2c_smbus.c
+++ b/drivers/input/mouse/elan_i2c_smbus.c
@@ -56,7 +56,7 @@
 static int elan_smbus_initialize(struct i2c_client *client)
 {
 	u8 check[ETP_SMBUS_HELLOPACKET_LEN] = { 0x55, 0x55, 0x55, 0x55, 0x55 };
-	u8 values[ETP_SMBUS_HELLOPACKET_LEN] = { 0, 0, 0, 0, 0 };
+	u8 values[I2C_SMBUS_BLOCK_MAX] = {0};
 	int len, error;
 
 	/* Get hello packet */
@@ -117,12 +117,16 @@ static int elan_smbus_calibrate(struct i2c_client *client)
 static int elan_smbus_calibrate_result(struct i2c_client *client, u8 *val)
 {
 	int error;
+	u8 buf[I2C_SMBUS_BLOCK_MAX] = {0};
+
+	BUILD_BUG_ON(ETP_CALIBRATE_MAX_LEN > sizeof(buf));
 
 	error = i2c_smbus_read_block_data(client,
-					  ETP_SMBUS_CALIBRATE_QUERY, val);
+					  ETP_SMBUS_CALIBRATE_QUERY, buf);
 	if (error < 0)
 		return error;
 
+	memcpy(val, buf, ETP_CALIBRATE_MAX_LEN);
 	return 0;
 }
 
@@ -472,6 +476,8 @@ static int elan_smbus_get_report(struct i2c_client *client, u8 *report)
 {
 	int len;
 
+	BUILD_BUG_ON(I2C_SMBUS_BLOCK_MAX > ETP_SMBUS_REPORT_LEN);
+
 	len = i2c_smbus_read_block_data(client,
 					ETP_SMBUS_PACKET_QUERY,
 					&report[ETP_SMBUS_REPORT_OFFSET]);
-- 
2.18.0