[CRIU] [PATCH] sysctl: restore sysctls for correct namespaces

[Tycho Andersen]

On Thu, Oct 08, 2015 at 05:03:53PM +0300, Andrey Vagin wrote:
> From: Andrew Vagin <avagin at openvz.org>
> 
> When we don't use userns, __userns_sysctl_op is called
> in context of the current process. A mount namespaces is restored
> the last one, so when we restore namespaces, we see /proc from the
> host pid namespace. In this case we can't use virtual pid to access
> /proc/pid.
> 
> Let's open /proc/self/ns and use this descriptor to switch namespaces.
> 
> Cc: Tycho Andersen <tycho.andersen at canonical.com>

Acked-by: Tycho Andersen <tycho.andersen at canonical.com>

Thanks.

> Fixes: f79f4546cfc0 ("sysctl: move sysctl calls to usernsd")
> Signed-off-by: Andrew Vagin <avagin at openvz.org>
> ---
>  sysctl.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/sysctl.c b/sysctl.c
> index f68dbe5..7dd08ba 100644
> --- a/sysctl.c
> +++ b/sysctl.c
> @@ -192,7 +192,7 @@ static int do_sysctl_op(int fd, struct sysctl_req *req, int op)
>  	return ret;
>  }
>  
> -static int __userns_sysctl_op(void *arg, int unused, pid_t pid)
> +static int __userns_sysctl_op(void *arg, int proc_fd, pid_t pid)
>  {
>  	int fd, ret = -1, dir, i, status, *fds = NULL;
>  	struct sysctl_userns_req *userns_req = arg;
> @@ -288,7 +288,7 @@ static int __userns_sysctl_op(void *arg, int unused, pid_t pid)
>  		const char *nsname = ns_to_string(userns_req->ns);
>  
>  		BUG_ON(!nsname);
> -		nsfd = open_proc(pid, "ns/%s", nsname);
> +		nsfd = openat(proc_fd, nsname, O_RDONLY);
>  		if (nsfd < 0) {
>  			pr_perror("failed to open pid %d's ns %s", pid, nsname);
>  			exit(1);
> @@ -382,7 +382,7 @@ out:
>  
>  int sysctl_op(struct sysctl_req *req, size_t nr_req, int op, unsigned int ns)
>  {
> -	int i;
> +	int i, fd, ret;
>  	struct sysctl_userns_req *userns_req;
>  	struct sysctl_req *cur;
>  
> @@ -453,5 +453,11 @@ int sysctl_op(struct sysctl_req *req, size_t nr_req, int op, unsigned int ns)
>  		cur = (struct sysctl_req *) (((char *) cur) + total_len);
>  	}
>  
> -	return userns_call(__userns_sysctl_op, UNS_ASYNC, userns_req, MAX_UNSFD_MSG_SIZE, -1);
> +	fd = open_proc(PROC_SELF, "ns");
> +	if (fd < 0)
> +		return -1;
> +
> +	ret = userns_call(__userns_sysctl_op, UNS_ASYNC, userns_req, MAX_UNSFD_MSG_SIZE, fd);
> +	close(fd);
> +	return ret;
>  }
> -- 
> 2.4.3
>