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

[Eric Blake <eblake@redhat.com>]

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)

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org