Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG not closing the fd

[David Hildenbrand]

On 13.10.21 11:48, Stefan Hajnoczi wrote:
> On Tue, Oct 12, 2021 at 08:38:32PM +0200, David Hildenbrand wrote:
> > We end up not closing the file descriptor, resulting in leaking one
> > file descriptor for each VHOST_USER_REM_MEM_REG message.
> >
> > Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> > Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Coiby Xu <coiby.xu@gmail.com>
> > Signed-off-by: David Hildenbrand <david@redhat.com>
> > ---
> >   subprojects/libvhost-user/libvhost-user.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/subprojects/libvhost-user/libvhost-user.c 
> > b/subprojects/libvhost-user/libvhost-user.c
> > index bf09693255..bb5c3b3280 100644
> > --- a/subprojects/libvhost-user/libvhost-user.c
> > +++ b/subprojects/libvhost-user/libvhost-user.c
> > @@ -839,6 +839,8 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> >           vu_panic(dev, "Specified region not found\n");
> >       }
> >   
> > +    close(vmsg->fds[0]);
>
> Does anything check that exactly 1 fd was received? For example,
> vu_set_log_fd_exec() does:
>
>    if (vmsg->fd_num != 1) {
>        vu_panic(dev, "Invalid log_fd message");
>        return false;
>    }
>
> I think that's necessary both to make vhost-user master development
> easier and because fds[] is not initialized to -1.

Similarly, vu_add_mem_reg() assumes exactly one was sent AFAIKS.

If we panic, do we still have to call vmsg_close_fds() ?

--
Thanks,

David / dhildenb