HID: cp2112: prevent a buffer overflow in cp2112_xfer()

Smatch warnings:
drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy()
'data->block[1]' too small (33 vs 255)
drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy() 'buf' too
small (64 vs 255)

The 'read_length' variable is provided by 'data->block[0]' which comes
from user and it(read_length) can take a value between 0-255. Add an
upper bound to 'read_length' variable to prevent a buffer overflow in
memcpy().

Fixes: 1bea6f7972d6 ("HID: cp2112: Fix I2C_BLOCK_DATA transactions")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
index ece147d1a278989e5655e14c178754726b3fd4b8..1e16b0fa310d16994b61845df5428fe007ac6693 100644 (file)
--- a/drivers/hid/hid-cp2112.c
+++ b/drivers/hid/hid-cp2112.c
@@ -790,6 +790,11 @@ static int cp2112_xfer(struct i2c_adapter *adap, u16 addr,
                data->word = le16_to_cpup((__le16 *)buf);
                break;
        case I2C_SMBUS_I2C_BLOCK_DATA:
+               if (read_length > I2C_SMBUS_BLOCK_MAX) {
+                       ret = -EINVAL;
+                       goto power_normal;
+               }
+
                memcpy(data->block + 1, buf, read_length);
                break;
        case I2C_SMBUS_BLOCK_DATA: