Re: [Qemu-trivial] [Qemu-devel] [PATCH] vt82c686: fix coverity warning about out-of-bounds write

[Stefan Weil <sw@weilnetz.de>]

Am 09.12.2014 um 06:44 schrieb zhanghailiang:
> Refactor superio_ioport_writeb to fix the out of bounds write warning.
> 
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>  hw/isa/vt82c686.c | 39 ++++++++++++++++++---------------------
>  1 file changed, 18 insertions(+), 21 deletions(-)
> 
> diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
> index e0c235c..4516af0 100644
> --- a/hw/isa/vt82c686.c
> +++ b/hw/isa/vt82c686.c
> @@ -50,13 +50,13 @@ typedef struct VT82C686BState {
>  static void superio_ioport_writeb(void *opaque, hwaddr addr, uint64_t data,
>                                    unsigned size)
>  {
> -    int can_write;
>      SuperIOConfig *superio_conf = opaque;
>  
>      DPRINTF("superio_ioport_writeb  address 0x%x  val 0x%x\n", addr, data);
>      if (addr == 0x3f0) {
>          superio_conf->index = data & 0xff;
>      } else {
> +        int can_write = 1;


IMHO using bool instead of int would be better here (and false, true in
the following code).

>          /* 0x3f1 */
>          switch (superio_conf->index) {
>          case 0x00 ... 0xdf:
> @@ -70,28 +70,25 @@ static void superio_ioport_writeb(void *opaque, hwaddr addr, uint64_t data,
>          case 0xfd ... 0xff:
>              can_write = 0;
>              break;
> -        default:
> -            can_write = 1;
> -
> -            if (can_write) {
> -                switch (superio_conf->index) {
> -                case 0xe7:
> -                    if ((data & 0xff) != 0xfe) {
> -                        DPRINTF("chage uart 1 base. unsupported yet\n");
> -                    }
> -                    break;
> -                case 0xe8:
> -                    if ((data & 0xff) != 0xbe) {
> -                        DPRINTF("chage uart 2 base. unsupported yet\n");
> -                    }
> -                    break;
> -
> -                default:
> -                    superio_conf->config[superio_conf->index] = data & 0xff;
> -                }
> +        case 0xe7:
> +            if ((data & 0xff) != 0xfe) {
> +                DPRINTF("chage uart 1 base. unsupported yet\n");

This text looks strange. Maybe a typo?

> +                can_write = 0;
> +            }
> +            break;
> +        case 0xe8:
> +            if ((data & 0xff) != 0xbe) {
> +                DPRINTF("chage uart 2 base. unsupported yet\n");

This text looks strange. Maybe a typo?

> +                can_write = 0;
>              }
> +            break;
> +        default:
> +            break;
> +
> +        }
> +        if (can_write) {
> +            superio_conf->config[superio_conf->index] = data & 0xff;
>          }
> -        superio_conf->config[superio_conf->index] = data & 0xff;
>      }
>  }


Regards
Stefan