[systemd-devel] [PATCH] Handle Unix domain socket connections from outside our namespace

[Zbigniew Jędrzejewski-Szmek]

On Wed, Apr 16, 2014 at 06:39:07PM +0200, Eelco Dolstra wrote:
> NixOS uses Unix domain sockets for certain host <-> container
> interaction; i.e. the host connects to a socket visible in the
> container's directory tree, where the container uses a .socket unit to
> spawn the handler program on demand. This worked in systemd 203, but
> in 212 fails with "foo.socket failed to queue service startup job
> (Maybe the service file is missing or not a template unit?): No data
> available".
> 
> The reason is that getpeercred() now returns ENODATA if it can't get
> the PID of the client, which happens in this case because the client
> is not in the same PID namespace. Since getpeercred() is only used to
> generate the instance name, this patch simply handles ENODATA by
> creating an instance name "<nr>-unknown".
Applied, but I changed the order of clauses in the if, because the
thin 'return k' between the two asprintfs was bother me :)

Zbyszek

>                  k = getpeercred(fd, &ucred);
> -                if (k < 0)
> +                if (k == -ENODATA) {
> +                        /* This handles the case where somebody is
> +                         * connecting from another pid/uid namespace
> +                         * (e.g. from outside of our container). */
> +                        if (asprintf(&r,
> +                                     "%u-unknown",
> +                                     nr) < 0)
> +                                return -ENOMEM;
> +                }
> +                else if (k < 0)
>                          return k;
> -
> -                if (asprintf(&r,
> -                             "%u-%lu-%lu",
> -                             nr,
> -                             (unsigned long) ucred.pid,
> -                             (unsigned long) ucred.uid) < 0)
> -                        return -ENOMEM;
> -
> +                else {
> +                        if (asprintf(&r,
> +                                     "%u-%lu-%lu",
> +                                     nr,
> +                                     (unsigned long) ucred.pid,
> +                                     (unsigned long) ucred.uid) < 0)
> +                                return -ENOMEM;
> +                }
>                  break;
>          }
>  
> -- 
> 1.9.0
> 
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