Re: [PATCH] tools/virtiofsd: add support for --socket-group

[Marc-André Lureau]

Hi

On Thu, Mar 12, 2020 at 11:49 AM Daniel P. Berrangé <address@hidden> wrote:
>
> On Thu, Mar 12, 2020 at 10:41:42AM +0000, Alex Bennée wrote:
> > If you like running QEMU as a normal user (very common for TCG runs)
> > but you have to run virtiofsd as a root user you run into connection
> > problems. Adding support for an optional --socket-group allows the
> > users to keep using the command line.
>
> If we're going to support this, then I think we need to put it in
> the vhost-user.rst specification so we standardize across backends.
>
>

Perhaps. Otoh, I wonder if the backend spec should be more limited to
arguments/introspection that are used by programs.

In this case, I even consider --socket-path to be unnecessary, as a
management layer can/should provide a preopened & setup fd directly.

What do you think?

>
> > Signed-off-by: Alex Bennée <address@hidden>
>
>
> >
> > ---
> > v1
> >   - tweak documentation and commentary
> > ---
> >  docs/tools/virtiofsd.rst        |  4 ++++
> >  tools/virtiofsd/fuse_i.h        |  1 +
> >  tools/virtiofsd/fuse_lowlevel.c |  6 ++++++
> >  tools/virtiofsd/fuse_virtio.c   | 20 ++++++++++++++++++--
> >  4 files changed, 29 insertions(+), 2 deletions(-)
> >
> > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > index 378594c422a..5a8246b74f8 100644
> > --- a/docs/tools/virtiofsd.rst
> > +++ b/docs/tools/virtiofsd.rst
> > @@ -85,6 +85,10 @@ Options
> >
> >    Listen on vhost-user UNIX domain socket at PATH.
> >
> > +.. option:: --socket-group=GROUP
> > +
> > +  Set the vhost-user UNIX domain socket gid to GROUP.
> > +
> >  .. option:: --fd=FDNUM
> >
> >    Accept connections from vhost-user UNIX domain socket file descriptor 
> > FDNUM.
> > diff --git a/tools/virtiofsd/fuse_i.h b/tools/virtiofsd/fuse_i.h
> > index 1240828208a..492e002181e 100644
> > --- a/tools/virtiofsd/fuse_i.h
> > +++ b/tools/virtiofsd/fuse_i.h
> > @@ -68,6 +68,7 @@ struct fuse_session {
> >      size_t bufsize;
> >      int error;
> >      char *vu_socket_path;
> > +    char *vu_socket_group;
> >      int   vu_listen_fd;
> >      int   vu_socketfd;
> >      struct fv_VuDev *virtio_dev;
> > diff --git a/tools/virtiofsd/fuse_lowlevel.c 
> > b/tools/virtiofsd/fuse_lowlevel.c
> > index 2dd36ec03b6..4d1ba2925d1 100644
> > --- a/tools/virtiofsd/fuse_lowlevel.c
> > +++ b/tools/virtiofsd/fuse_lowlevel.c
> > @@ -2523,6 +2523,7 @@ static const struct fuse_opt fuse_ll_opts[] = {
> >      LL_OPTION("--debug", debug, 1),
> >      LL_OPTION("allow_root", deny_others, 1),
> >      LL_OPTION("--socket-path=%s", vu_socket_path, 0),
> > +    LL_OPTION("--socket-group=%s", vu_socket_group, 0),
> >      LL_OPTION("--fd=%d", vu_listen_fd, 0),
> >      LL_OPTION("--thread-pool-size=%d", thread_pool_size, 0),
> >      FUSE_OPT_END
> > @@ -2630,6 +2631,11 @@ struct fuse_session *fuse_session_new(struct 
> > fuse_args *args,
> >                   "fuse: --socket-path and --fd cannot be given 
> > together\n");
> >          goto out4;
> >      }
> > +    if (se->vu_socket_group && !se->vu_socket_path) {
> > +        fuse_log(FUSE_LOG_ERR,
> > +                 "fuse: --socket-group can only be used with 
> > --socket-path\n");
> > +        goto out4;
> > +    }
> >
> >      se->bufsize = FUSE_MAX_MAX_PAGES * getpagesize() + 
> > FUSE_BUFFER_HEADER_SIZE;
> >
> > diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
> > index 3b6d16a0417..331f9fc65c5 100644
> > --- a/tools/virtiofsd/fuse_virtio.c
> > +++ b/tools/virtiofsd/fuse_virtio.c
> > @@ -31,6 +31,8 @@
> >  #include <sys/socket.h>
> >  #include <sys/types.h>
> >  #include <sys/un.h>
> > +#include <sys/types.h>
> > +#include <grp.h>
> >  #include <unistd.h>
> >
> >  #include "contrib/libvhost-user/libvhost-user.h"
> > @@ -924,15 +926,29 @@ static int fv_create_listen_socket(struct 
> > fuse_session *se)
> >
> >      /*
> >       * Unfortunately bind doesn't let you set the mask on the socket,
> > -     * so set umask to 077 and restore it later.
> > +     * so set umask appropriately and restore it later.
> >       */
> > -    old_umask = umask(0077);
> > +    if (se->vu_socket_group) {
> > +        old_umask = umask(S_IROTH | S_IWOTH | S_IXOTH);
> > +    } else {
> > +        old_umask = umask(S_IRGRP | S_IWGRP | S_IXGRP | S_IROTH | S_IWOTH 
> > | S_IXOTH);
> > +    }
> >      if (bind(listen_sock, (struct sockaddr *)&un, addr_len) == -1) {
> >          fuse_log(FUSE_LOG_ERR, "vhost socket bind: %m\n");
> >          close(listen_sock);
> >          umask(old_umask);
> >          return -1;
> >      }
> > +    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)) {
> > +                fuse_log(FUSE_LOG_WARNING,
> > +                         "vhost socket failed to set group to %s (%d)\n",
> > +                         se->vu_socket_group, g->gr_gid);
> > +            }
> > +        }
> > +    }
> >      umask(old_umask);
> >
> >      if (listen(listen_sock, 1) == -1) {
> > --
> > 2.20.1
> >
> >
>
> Regards,
> Daniel
> --
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>
>


-- 
Marc-André Lureau