re: mtd: rawnand: add NVIDIA Tegra NAND Flash controller driver

[Colin Ian King <colin.king@canonical.com>]

Hi there,

Static analysis with CoverityScan reported a potential issue with the
following commit:

commit 0f7b126ca91101d02d525f7cc880e8c71202a2b7
Author: Stefan Agner <stefan@agner.ch>
Date:   Sun Jun 24 23:27:25 2018 +0200

    mtd: rawnand: add NVIDIA Tegra NAND Flash controller driver


in function tegra_nand_cmd it looks like there maybe potential to pass a
negative value in size into memcpy():

        case NAND_OP_DATA_OUT_INSTR:

negative_return_fn: Function nand_subop_get_data_len(subop, op_id)
returns a negative number.

var_assign: Assigning: unsigned variable size = nand_subop_get_data_len.

                size = nand_subop_get_data_len(subop, op_id);
                offset = nand_subop_get_data_start_off(subop, op_id);

                cmd |= COMMAND_TRANS_SIZE(size) | COMMAND_PIO |
                        COMMAND_TX | COMMAND_A_VALID;

Argument cannot be negative (NEGATIVE_RETURNS)65. negative_returns: size
is passed to a parameter that cannot be negative.
                memcpy(&reg, instr->ctx.data.buf.out + offset, size);


I also think the same issue may be happening with the
NAND_OP_DATA_IN_INSTR case too.

Colin