[CRIU] [PATCH 5/5] userns: restore gid and uid maps

[Andrew Vagin]

On Tue, Feb 11, 2014 at 08:50:35AM +0400, Pavel Emelyanov wrote:
> > +static int write_id_map(pid_t pid, UidGidExtent **extents, int n, char *id_map)
> > +{
> > +	char buf[PAGE_SIZE];
> > +	int off = 0, i;
> > +	int fd;
> > +
> > +	for (i = 0; i < n; i++)
> > +		off += snprintf(buf + off, sizeof(buf) - off,
> > +				"%d %d %d", extents[i]->first,
> > +					extents[i]->lower_first,
> > +					extents[i]->count);
> 
> Maybe use fopen_proc for that? This would avoid allocating
> one more buffer on the stack.

* We don't have fopen_proc_rw
* {u,g}id_map files can be written only once

so we can't use stream here.

> 
> > +
> > +	fd = open_proc_rw(pid, "%s", id_map);
> > +	if (fd < 0)
> > +		return -1;
> > +	if (write(fd, buf, off) != off) {
> > +		pr_perror("Unable to write into %s\n", id_map);
> > +		close(fd);
> > +		return -1;
> > +	}
> > +	close(fd);
> > +
> > +	return 0;
> > +}
> > +
> > +int prepare_userns(struct pstree_item *item)
> > +{
> > +	UsernsEntry *e;
> > +	int fd, ret;
> > +
> > +	fd = open_image(CR_FD_USERNS, O_RSTR, item->ids->user_ns_id);
> > +	ret = pb_read_one(fd, &e, PB_USERNS);
> > +	close(fd);
> > +	if (ret < 0)
> > +		return -1;
> > +
> > +	if (write_id_map(item->pid.real, e->uid_map, e->n_uid_map, "uid_map"))
> > +		return -1;
> > +
> > +	if (write_id_map(item->pid.real, e->gid_map, e->n_gid_map, "gid_map"))
> > +		return -1;
> > +
> > +	return 0;
> > +}
> > +
> >  int prepare_namespace(struct pstree_item *item, unsigned long clone_flags)
> >  {
> >  	pid_t pid = item->pid.virt;
> > 
> 
>