Re: [Qemu-devel] [PATCH v4 2/4] hw/core: rebase sysbus_get_fw_dev_path() to g_strdup_printf()

[Markus Armbruster]

Laszlo Ersek <address@hidden> writes:

> Cc: Markus Armbruster <address@hidden>
> Cc: Marcel Apfelbaum <address@hidden>
> Cc: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Laszlo Ersek <address@hidden>
> ---
>
> Notes:
>     v4:
>     - unchanged
>     
>     v3:
>     - new in v3
>
>  hw/core/sysbus.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
> index b53c351..0ebb4e2 100644
> --- a/hw/core/sysbus.c
> +++ b/hw/core/sysbus.c
> @@ -281,19 +281,15 @@ static void sysbus_dev_print(Monitor *mon, DeviceState 
> *dev, int indent)
>  static char *sysbus_get_fw_dev_path(DeviceState *dev)
>  {
>      SysBusDevice *s = SYS_BUS_DEVICE(dev);
> -    char path[40];
> -    int off;
> -
> -    off = snprintf(path, sizeof(path), "%s", qdev_fw_name(dev));
>  
>      if (s->num_mmio) {
> -        snprintf(path + off, sizeof(path) - off, "@"TARGET_FMT_plx,
> -                 s->mmio[0].addr);
> -    } else if (s->num_pio) {
> -        snprintf(path + off, sizeof(path) - off, "@i%04x", s->pio[0]);
> +        return g_strdup_printf("%s@"TARGET_FMT_plx, qdev_fw_name(dev),

I'd put a space between "%s@" and TARGET_FMT_plx.

> +                               s->mmio[0].addr);
>      }
> -
> -    return g_strdup(path);
> +    if (s->num_pio) {
> +        return g_strdup_printf("address@hidden", qdev_fw_name(dev), 
> s->pio[0]);
> +    }
> +    return g_strdup(qdev_fw_name(dev));
>  }
>  
>  void sysbus_add_io(SysBusDevice *dev, hwaddr addr,

Would be nice if we didn't have to triplicate qdev_fw_name(), but I
don't have better ideas.

Bonus: no arbitrary length limit.  Before your patch, it's 39
characters, and the code breaks catastrophically when qdev_fw_name() is
longer: the second snprintf() is called with its first argument pointing
beyond path[], and its second argument underflowing to a huge size.
Textbook example of how not to use snprintf().  Worth mentioning in the
commit message?

Reviewed-by: Markus Armbruster <address@hidden>