[CRIU] [PATCH] fs: Opening FE-s after fchdir doesn't work

[Andrew Vagin]

Acked-by: Andrew Vagin <avagin at parallels.com>

On Mon, Jun 09, 2014 at 04:51:16PM +0400, Pavel Emelyanov wrote:
> It uses absolute file names, so any open-s should happen _before_
> we change tasks' root.
> 
> Signed-off-by: Pavel Emelyanov <xemul at parallels.com>
> ---
>  files.c | 31 +++++++++++++++++--------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/files.c b/files.c
> index a8cd87f..18d0f97 100644
> --- a/files.c
> +++ b/files.c
> @@ -1020,7 +1020,7 @@ static int fchroot(int fd)
>  
>  int prepare_fs(int pid)
>  {
> -	int ifd, dd, ret, err = -1;
> +	int ifd, dd_root, dd_cwd, ret, err = -1;
>  	FsEntry *fe;
>  
>  	ifd = open_image(CR_FD_FS, O_RSTR, pid);
> @@ -1031,34 +1031,37 @@ int prepare_fs(int pid)
>  		goto out_i;
>  
>  	/*
> -	 * Restore root
> +	 * First -- open both descriptors. We will not
> +	 * be able to open the cwd one after we chroot.
>  	 */
>  
> -	dd = open_reg_by_id(fe->root_id);
> -	if (dd < 0) {
> +	dd_root = open_reg_by_id(fe->root_id);
> +	if (dd_root < 0) {
>  		pr_err("Can't open root %#x\n", fe->root_id);
>  		goto err;
>  	}
>  
> -	ret = fchroot(dd);
> -	close(dd);
> -	if (ret < 0) {
> -		pr_perror("Can't change root");
> +	dd_cwd = open_reg_by_id(fe->cwd_id);
> +	if (dd_cwd < 0) {
> +		pr_err("Can't open cwd %#x\n", fe->cwd_id);
>  		goto err;
>  	}
>  
>  	/*
> -	 * Restore CWD
> +	 * Now do chroot/chdir. Chroot goes first as it
> +	 * calls chdir into proc service descriptor so
> +	 * we'd need to fix chdir after it anyway.
>  	 */
>  
> -	dd = open_reg_by_id(fe->cwd_id);
> -	if (dd < 0) {
> -		pr_err("Can't open cwd %#x\n", fe->cwd_id);
> +	ret = fchroot(dd_root);
> +	close(dd_root);
> +	if (ret < 0) {
> +		pr_perror("Can't change root");
>  		goto err;
>  	}
>  
> -	ret = fchdir(dd);
> -	close(dd);
> +	ret = fchdir(dd_cwd);
> +	close(dd_cwd);
>  	if (ret < 0) {
>  		pr_perror("Can't change cwd");
>  		goto err;
> -- 
> 1.8.4.2
> _______________________________________________
> CRIU mailing list
> CRIU at openvz.org
> https://lists.openvz.org/mailman/listinfo/criu