Re: [PATCH] xl: Return an error if an empty file is passed to cd-insert

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

On 10/05/13 17:43, George Dunlap wrote:
> Two changes:
> * Stat the file before calling libxl_cdrom_insert()
> * Return an error if anything fails (including libxl_cdrom_insert)
> 
> This is in part to work around the fact that the RAW disk type
> is used for things that aren't actually files; so we can't call
> stat in libxl_device.c:libxl__device_disk_set_backend() because
> it may be going over a remote protocol.
> 
> Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
> CC: Ian Campbell <ian.campbell@citrix.com>
> CC: Ian Jackson <ian.jackson@citrix.com>
> ---
>  tools/libxl/xl_cmdimpl.c |   26 +++++++++++++++++++++-----
>  1 file changed, 21 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> index c1a969b..e8ce35b 100644
> --- a/tools/libxl/xl_cmdimpl.c
> +++ b/tools/libxl/xl_cmdimpl.c
> @@ -2505,25 +2505,42 @@ int main_memset(int argc, char **argv)
>      return 0;
>  }
>  
> -static void cd_insert(uint32_t domid, const char *virtdev, char *phys)
> +static int cd_insert(uint32_t domid, const char *virtdev, char *phys)
>  {
>      libxl_device_disk disk; /* we don't free disk's contents */
>      char *buf = NULL;
>      XLU_Config *config = 0;
> +    struct stat b;
> +    int rc = 0;
>  
>  
>      if (asprintf(&buf, "vdev=%s,access=r,devtype=cdrom,target=%s",
>                   virtdev, phys ? phys : "") < 0) {
>          fprintf(stderr, "out of memory\n");
> -        return;
> +        return 1;

ERROR_NOMEM

>      }
>  
>      parse_disk_config(&config, buf, &disk);
>  
> -    libxl_cdrom_insert(ctx, domid, &disk, NULL);
> +    /* ATM the existence of the backing file is not checked for qdisk
> +     * in libxl_cdrom_insert() because RAW is used for remote
> +     * protocols as well as plain files.  This will ideally be changed
> +     * for 4.4, but this work-around fixes the problem of "cd-insert"
> +     * returning success for non-existent files. */
> +    if (disk.format != LIBXL_DISK_FORMAT_EMPTY
> +        && stat(disk.pdev_path, &b)) {
> +        fprintf(stderr, "Cannot stat file: %s\n",
> +                disk.pdev_path);

You are leaking buf here, I know xl is just about to exit, but it might
be best to to define a label below that contains:

out:
    free(buf);
    return rc;


and go to it.

> +        return 1;

ERROR_INVAL

> +    }
> +
> +    if (libxl_cdrom_insert(ctx, domid, &disk, NULL))
> +        rc=1;

You could use the return value of libxl_cdrom_insert instead of 1.

>  
>      libxl_device_disk_dispose(&disk);
>      free(buf);
> +
> +    return rc;
>  }
>  
>  int main_cd_eject(int argc, char **argv)
> @@ -2539,8 +2556,7 @@ int main_cd_eject(int argc, char **argv)
>      domid = find_domain(argv[optind]);
>      virtdev = argv[optind + 1];
>  
> -    cd_insert(domid, virtdev, NULL);
> -    return 0;
> +    return cd_insert(domid, virtdev, NULL);
>  }
>  
>  int main_cd_insert(int argc, char **argv)
>