[lxc-devel] [PATCH 6/6] c/r: use mkstemp to get a pidfile name

[Stéphane Graber]

On Mon, Apr 13, 2015 at 06:07:05PM +0000, Tycho Andersen wrote:
> This is more secure than tempnam().

No such thing as mkstemp on Android unfortunately.

> 
> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> ---
>  src/lxc/lxccontainer.c | 30 +++++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> index 5b96b8c..8424cf6 100644
> --- a/src/lxc/lxccontainer.c
> +++ b/src/lxc/lxccontainer.c
> @@ -4128,12 +4128,30 @@ out_unlock:
>  static void do_restore(struct lxc_container *c, int pipe, char *directory, bool verbose)
>  {
>  	pid_t pid;
> -	char pidfile[L_tmpnam];
> +	char pidfile[sizeof(P_tmpdir) + 25];
>  	struct lxc_handler *handler;
> -	int status;
> +	int status, ret;
> +
> +	ret = snprintf(pidfile, sizeof(pidfile), "%s/lxc_criu_pidfile.XXXXXX", P_tmpdir);
> +	if (ret < 0 || ret >= sizeof(pidfile))
> +		goto out;
> +
> +	/*
> +	 * Here, we simply use mkstemp to acquire a secure tmpfile name. CRIU
> +	 * tries to create the pidfile with O_CREAT | O_EXCL, so we need to
> +	 * remove it before calling criu.
> +	 */
> +	ret = mkstemp(pidfile);
> +	if (ret < 0) {
> +		SYSERROR("failed to create pidfile");
> +		goto out;
> +	}
>  
> -	if (!tmpnam(pidfile))
> +	close(ret);
> +	if (remove(pidfile) < 0) {
> +		SYSERROR("failed to remove pidfile");
>  		goto out;
> +	}
>  
>  	handler = lxc_init(c->name, c->lxc_conf, c->config_path);
>  	if (!handler)
> @@ -4231,6 +4249,12 @@ static void do_restore(struct lxc_container *c, int pipe, char *directory, bool
>  
>  				ret = fscanf(f, "%d", (int*) &handler->pid);
>  				fclose(f);
> +
> +				if (remove(pidfile) < 0) {
> +					SYSERROR("failed to remove pidfile");
> +					goto out_fini_handler;
> +				}
> +
>  				if (ret != 1) {
>  					ERROR("reading restore pid failed");
>  					goto out_fini_handler;
> -- 
> 2.1.4
> 
> _______________________________________________
> lxc-devel mailing list
> lxc-devel at lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-devel

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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