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

[Stefan Hajnoczi <stefanha@redhat.com>]

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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.

Stefan

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