i2c: ismt: prevent memory corruption in ismt_access()

The "data->block[0]" variable comes from the user and is a number
between 0-255.  It needs to be capped to prevent writing beyond the end
of dma_buffer[].

Fixes: 5e9a97b1f449 ("i2c: ismt: Adding support for I2C_SMBUS_BLOCK_PROC_CALL")
Reported-and-tested-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c
index c16157e..6078fa0 100644 (file)
--- a/drivers/i2c/busses/i2c-ismt.c
+++ b/drivers/i2c/busses/i2c-ismt.c
@@ -528,6 +528,9 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
 
        case I2C_SMBUS_BLOCK_PROC_CALL:
                dev_dbg(dev, "I2C_SMBUS_BLOCK_PROC_CALL\n");
+               if (data->block[0] > I2C_SMBUS_BLOCK_MAX)
+                       return -EINVAL;
+
                dma_size = I2C_SMBUS_BLOCK_MAX;
                desc->tgtaddr_rw = ISMT_DESC_ADDR_RW(addr, 1);
                desc->wr_len_cmd = data->block[0] + 1;