Re: [Qemu-devel] [PATCH 17/28] ahci: construct PIO Setup FIS for PIO commands

[Stefan Hajnoczi]

On Mon, Jul 07, 2014 at 02:17:58PM -0400, John Snow wrote:
> +static void ahci_write_fis_pio(AHCIDevice *ad, uint16_t len)
> +{
> +    AHCIPortRegs *pr = &ad->port_regs;
> +    uint8_t *pio_fis, *cmd_fis;
> +    uint64_t tbl_addr;
> +    dma_addr_t cmd_len = 0x80;
> +
> +    if (!ad->res_fis || !(pr->cmd & PORT_CMD_FIS_RX)) {
> +        return;
> +    }
> +
> +    /* map cmd_fis */
> +    tbl_addr = le64_to_cpu(ad->cur_cmd->tbl_addr);
> +    cmd_fis = dma_memory_map(ad->hba->as, tbl_addr, &cmd_len,
> +                             DMA_DIRECTION_TO_DEVICE);

We should check cmd_len == 0x80 and cmd_fis != NULL to avoid undefined
behavior when accessing cmd_fis.

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