[PATCH 1/3] Input: elan_i2c_smbus - cast sizeof to int for comparison

Julia Lawall
2018-07-01T17:32:03Z

Comparing an int to a size, which is unsigned, causes the int to become
unsigned, giving the wrong result. i2c_smbus_read_block_data can return the
result of i2c_smbus_xfer, whih can return a negative error code.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
int x;
expression e,e1;
identifier f;
@@

*x = f(...);
... when != x = e1
when != if (x < 0 || ...) { ... return ...; }
*x < sizeof(e)
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>

---
drivers/input/mouse/elan_i2c_smbus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/mouse/elan_i2c_smbus.c b/drivers/input/mouse/elan_i2c_smbus.c
index c060d27..88e315d 100644
--- a/drivers/input/mouse/elan_i2c_smbus.c
+++ b/drivers/input/mouse/elan_i2c_smbus.c
@@ -387,7 +387,7 @@ static int elan_smbus_prepare_fw_update(struct i2c_client *client)
len = i2c_smbus_read_block_data(client,
ETP_SMBUS_IAP_PASSWORD_READ,
val);
- if (len < sizeof(u16)) {
+ if (len < (int)sizeof(u16)) {
error = len < 0 ? len : -EIO;
dev_err(dev, "failed to read iap password: %d\n",
error);