Input: elan_i2c_smbus - fix more potential stack buffer overflows

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>

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]);