[CRIU] [PATCH] tmpfs: don't try to dump mountpoint at 0 fd

[Andrew Vagin]

On Tue, Jan 19, 2016 at 09:15:05AM -0700, Tycho Andersen wrote:
> If we happen to get 0 as the fd for the mountpoint, there is an error:
> 
> (00.280617) Dumping task cwd id 0x2b root id 0x2b
> (00.280697) mnt: Dumping mountpoints
> (00.280702) mnt:        132: 34:/ @ ./run/lock
> (00.280714) mnt: Path `/run/lock' resolved to `./run/lock' mountpoint
> tar: /proc/self/fd/0: Cannot open: Not a directory
> tar: Error is not recoverable: exiting now
> (00.283581) Error (util.c:666): exited, status=2
> (00.283598) Error (mount.c:1220): mnt: Can't dump tmpfs content
> 
> Instead, let's not ever use 0 as the mountpoint fd.
> 
> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> ---
>  mount.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/mount.c b/mount.c
> index 9d5667a..ae7bfae 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -1190,6 +1190,13 @@ static int tmpfs_dump(struct mount_info *pm)
>  	if (fd < 0)
>  		return -1;
>  
> +	/* if fd happens to be 0 here, we need to move it to something
> +	 * non-zero, because cr_system_userns closes STDIN_FILENO as we are not
> +	 * interested in passing stdin to tar.
> +	 */
> +	if (move_img_fd(&fd, STDIN_FILENO) < 0)
> +		goto out;

Should we handle a case when fd is equal to STDOUT_FILENO or
STDERR_FILENO?
> +
>  	if (fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) & ~FD_CLOEXEC) == -1) {
>  		pr_perror("Can not drop FD_CLOEXEC");
>  		goto out;
> -- 
> 2.7.0.rc3
> 
> _______________________________________________
> CRIU mailing list
> CRIU at openvz.org
> https://lists.openvz.org/mailman/listinfo/criu