Re: [PATCH] virtiofsd: Fix check of chown()'s return value

[Greg Kurz <groug@kaod.org>]

On Fri, 7 May 2021 11:19:07 -0500
Eric Blake <eblake@redhat.com> wrote:

> On 5/7/21 11:12 AM, Greg Kurz wrote:
> > Otherwise you always get this warning when using --socket-group=users
> > 
> >  vhost socket failed to set group to users (100)
> > 
> > While here, print out the error if chown() fails.
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>
> > ---
> >  tools/virtiofsd/fuse_virtio.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
> > index 3e13997406bf..638d3ffe2f8a 100644
> > --- a/tools/virtiofsd/fuse_virtio.c
> > +++ b/tools/virtiofsd/fuse_virtio.c
> > @@ -978,9 +978,9 @@ static int fv_create_listen_socket(struct fuse_session *se)
> >      if (se->vu_socket_group) {
> >          struct group *g = getgrnam(se->vu_socket_group);
> >          if (g) {
> > -            if (!chown(se->vu_socket_path, -1, g->gr_gid)) {
> > +            if (chown(se->vu_socket_path, -1, g->gr_gid) == -1) {
> >                  fuse_log(FUSE_LOG_WARNING,
> > -                         "vhost socket failed to set group to %s (%d)\n",
> > +                         "vhost socket failed to set group to %s (%d): %m\n",
> 
> Is %m portable?  POSIX requires it for syslog, but not for printf (where
> glibc has it as an extension), but I'm not sure what fuse_log supports.
> Best might be a manual %s/strerror(errno)
> 

virtiofsd is for linux+glibc only and %m is already used a few lines
above in the same function.