Re: [Libguestfs] [PATCH 1/3] launch: add internal helper for socket paths creation

Richard W.M. Jones
Wed, 03 Feb 2016 10:41:06 -0000

On Wed, Feb 03, 2016 at 10:34:06AM +0000, Richard W.M. Jones
wrote:
> On Wed, Feb 03, 2016 at 10:35:07AM +0100, Pino Toscano wrote:
> > On Tuesday 02 February 2016 19:47:12 Richard W.M. Jones wrote:
> > > On Tue, Feb 02, 2016 at 03:27:39PM +0100, Pino Toscano wrote:
> > > > diff --git a/src/launch.c b/src/launch.c
> > > > index f59818f..ec061e3 100644
> > > > --- a/src/launch.c
> > > > +++ b/src/launch.c
> > > > @@ -418,6 +418,21 @@ guestfs_int_get_cpu_model (int kvm)
> > > >  #endif
> > > >  }
> > > >
> > > > +/* Create the path for a socket with the selected filename
in the
> > > > + * tmpdir.
> > > > + */
> > > > +int
> > > > +guestfs_int_create_socketname (guestfs_h *g, const char
*filename,
> > > > +                               char
(*sockpath)[UNIX_PATH_MAX])
> > > > +{
> > > > +  char *path = g->tmpdir;
> > > > +
> > > > +  snprintf (*sockpath, UNIX_PATH_MAX-1, "%s/%s",
path, filename);
> > > > +  (*sockpath)[UNIX_PATH_MAX-1] = '\0';
> > >
> > > What's wrong with:
> > >
> > >   snprintf (*sockpath, UNIX_PATH_MAX, "%s/%s", path,
filename);
> >
> > If the "$path/$filename" string is longer than
UNIX_PATH_MAX, then
> > *sockpath won't be 0-terminated.
>
> That's not true though:

Having said that, what this function _could_ usefully do is to give a
fatal error if the final path is longer than UNIX_PATH_MAX-1, since
truncating the path is unlikely to produce correct behaviour.

Rich.

--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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