i2c: ismt: Return EMSGSIZE for block reads with bogus length

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>
Cc: stable@kernel.org

diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c
index 9af2337eb17a00f358b6386226c74260a852e1b0..22ffcb73c185f592d8b4e6bdbb1ede45cbeb4951 100644 (file)
--- 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;