Re: [Patch v2 3/4] tools/libxl: Fix libxl__device_nic_from_xs_be()

["Roger Pau Monné" <roger.pau@citrix.com>]

On 25/11/13 16:19, Andrew Cooper wrote:
> Coverity ID: 1055886
> 
> Replace uses of xs_read() with libxl__xs_read_checked() which appropriately
> garbage-collects the allocated string, and avoid executing
> libxl__parse_mac(NULL,) if the second xenstore read fails.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Ian Campbell <Ian.Campbell@citrix.com>
> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: Roger Pau Monne <roger.pau@citrix.com>
> 
> ---
> Changes in v2:
>  * Use libxl__xs_read_checked() in preference to xs_read() and free()
> ---
>  tools/libxl/libxl.c |   18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index 2b847ef..52f4c68 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -2982,24 +2982,24 @@ static void libxl__device_nic_from_xs_be(libxl__gc *gc,
>  {
>      libxl_ctx *ctx = libxl__gc_owner(gc);
>      unsigned int len;
> -    char *tmp;
> -    int rc;
> +    const char *tmp;
>  
>      libxl_device_nic_init(nic);
>  
> -    tmp = xs_read(ctx->xsh, XBT_NULL,
> -                  libxl__sprintf(gc, "%s/handle", be_path), &len);
> -    if ( tmp )
> +    if ( (libxl__xs_read_checked(gc, XBT_NULL,
> +                                 libxl__sprintf(gc, "%s/handle", be_path),
> +                                 &tmp) == 0) && strlen(tmp) )

libxl coding style doesn't add spaces between parentheses. Also,
consider using rc instead of directly checking the return value of the
function.

>          nic->devid = atoi(tmp);
>      else
>          nic->devid = 0;
>  
>      /* nic->mtu = */
>  
> -    tmp = xs_read(ctx->xsh, XBT_NULL,
> -                  libxl__sprintf(gc, "%s/mac", be_path), &len);
> -    rc = libxl__parse_mac(tmp, nic->mac);
> -    if (rc)
> +    if ( (libxl__xs_read_checked(gc, XBT_NULL,
> +                                 libxl__sprintf(gc, "%s/mac", be_path),
> +                                 &tmp) != 0) ||
> +         (strlen(tmp) == 0) ||
> +         (libxl__parse_mac(tmp, nic->mac) != 0) )

No inner spaces in parentheses and use rc to keep this if condition much
more readable IMHO.

Roger.

>          memset(nic->mac, 0, sizeof(nic->mac));
>  
>      nic->ip = xs_read(ctx->xsh, XBT_NULL,
>