[Libguestfs] [PATCH] lib: Better handling for problems creating the socket path

[Laszlo Ersek]

On 01/17/22 13:40, Richard W.M. Jones wrote:
> GCC 12 gives a warning about our previous attempt to check the length
> of the socket path.  In the ensuing discussion it was pointed out that
> it is easier to get snprintf to do the hard work.  snprintf will
> return an int >= UNIX_PATH_MAX if the path is too long, or -1 if there
> are other errors such as locale/encoding problems.  So we should just
> check for those two cases instead.
> 
> https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/thread/NPKWMTSJ2A2ABNJJEH6WTZIAEFTX6CQY/
> 
> Thanks: Martin Sebor and Laszlo Ersek
> ---
>  lib/launch.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/launch.c b/lib/launch.c
> index 253189b200..e3f64aec90 100644
> --- a/lib/launch.c
> +++ b/lib/launch.c
> @@ -325,15 +325,20 @@ int
>  guestfs_int_create_socketname (guestfs_h *g, const char *filename,
>                                 char (*sockpath)[UNIX_PATH_MAX])
>  {
> +  int r;
> +
>    if (guestfs_int_lazy_make_sockdir (g) == -1)
>      return -1;
>  
> -  if (strlen (g->sockdir) + 1 + strlen (filename) > UNIX_PATH_MAX-1) {
> +  r = snprintf (*sockpath, UNIX_PATH_MAX, "%s/%s", g->sockdir, filename);
> +  if (r >= UNIX_PATH_MAX) {
>      error (g, _("socket path too long: %s/%s"), g->sockdir, filename);
>      return -1;
>    }
> -
> -  snprintf (*sockpath, UNIX_PATH_MAX, "%s/%s", g->sockdir, filename);
> +  if (r == -1) {
> +    perrorf (g, _("%s"), g->sockdir);
> +    return -1;
> +  }
>  
>    return 0;
>  }
> 

The specs don't say (-1), they say "a negative value". I suggest
updating both the commit message and the last error check.

With that:

Reviewed-by: Laszlo Ersek <lersek at redhat.com>

Thanks,
Laszlo