[lxc-devel] Unprivilege containers do not work on kernel 3.14.8, 3.15.1
KATOH Yasufumi
karma at jazz.email.ne.jp
Wed Jun 25 08:37:12 UTC 2014
>>> On Tue, 24 Jun 2014 20:25:12 +0900
in message "Re: [lxc-devel] Unprivilege containers do not work on kernel 3.14.8, 3.15.1"
KATOH Yasufumi-san wrote:
> >>> On Mon, 23 Jun 2014 20:48:26 +0000
> in message "Re: [lxc-devel] Unprivilege containers do not work on kernel 3.14.8, 3.15.1"
> Serge Hallyn-san wrote:
> > Good point. So we'll have to cgroup the pty to our own gid before
> > we can do the userns chown. So
> > cgroup $(id -g) /dev/pts/3
s/cgroup/chgrp/ ? (^^;
> > lxc-usernsexec -m u:0:100000:1 -m u:$(id -u):1000:1 -m g:0:100000:1 -m g:$(id -g):1000:1 -- chown 0 /dev/pts/3
> > should do the trick. Until you hit the next roadblock :)
> TAMUKI-san(who maintained lxc-plamo) and I tried to make the patch
> :-), then unpriv container now work on my host. Please review it!
> But after container start, the console can't use. Is that reason that
> the group of tty (on container) or pty (on host) is not tty group? Do
> you have any idea?
I tried to resolv this, then
chgrp 100 /dev/pts/3
lxc-usernsexec -m u:0:100000:1 -m u:1000:1000:1 \
> -m g:0:100000:1 -m g:100:100:1 -m g:5:100005:1 \
> -- chown 0:5 /dev/pts/3
(My uid:gid = 1000:100, gid of tty = 5)
This works fine :-)
I updated the patch. After applying, foreground run of lxc-start and
lxc-console work fine. :-) Please review it:
From e2f2847b00ceea387c865c0104b1c6ed4a6fc7df Mon Sep 17 00:00:00 2001
From: KATOH Yasufumi <karma at jazz.email.ne.jp>
Date: Wed, 25 Jun 2014 17:21:10 +0900
Subject: [PATCH v2] Fix to work with unprivileged containers on recent kernel
Change chown_mapped_root() to map in both the root uid and gid, not
just the uid, so as to work with unprivileged containers on recent
kernel.
Signed-off-by: TAMUKI Shoichi <tamuki at linet.gr.jp>
Signed-off-by: KATOH Yasufumi <karma at jazz.email.ne.jp>
---
src/lxc/conf.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 55 insertions(+), 14 deletions(-)
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index c8b573a..83d7267 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -3338,7 +3338,7 @@ bool get_mapped_rootid(struct lxc_conf *conf, enum idtype idtype,
lxc_list_for_each(it, &conf->id_map) {
map = it->elem;
- if (map->idtype != ID_TYPE_UID)
+ if (map->idtype != idtype)
continue;
if (map->nsid != 0)
continue;
@@ -3500,7 +3500,8 @@ void lxc_delete_tty(struct lxc_tty_info *tty_info)
*/
int chown_mapped_root(char *path, struct lxc_conf *conf)
{
- uid_t rootid;
+ uid_t rootuid;
+ gid_t rootgid;
pid_t pid;
unsigned long val;
char *chownpath = path;
@@ -3509,7 +3510,12 @@ int chown_mapped_root(char *path, struct lxc_conf *conf)
ERROR("No mapping for container root");
return -1;
}
- rootid = (uid_t) val;
+ rootuid = (uid_t) val;
+ if (!get_mapped_rootid(conf, ID_TYPE_GID, &val)) {
+ ERROR("No mapping for container root");
+ return -1;
+ }
+ rootgid = (gid_t) val;
/*
* In case of overlay, we want only the writeable layer
@@ -3530,14 +3536,14 @@ int chown_mapped_root(char *path, struct lxc_conf *conf)
}
path = chownpath;
if (geteuid() == 0) {
- if (chown(path, rootid, -1) < 0) {
+ if (chown(path, rootuid, rootgid) < 0) {
ERROR("Error chowning %s", path);
return -1;
}
return 0;
}
- if (rootid == geteuid()) {
+ if (rootuid == geteuid()) {
// nothing to do
INFO("%s: container root is our uid; no need to chown" ,__func__);
return 0;
@@ -3549,13 +3555,27 @@ int chown_mapped_root(char *path, struct lxc_conf *conf)
return -1;
}
if (!pid) {
- int hostuid = geteuid(), ret;
- char map1[100], map2[100], map3[100];
- char *args[] = {"lxc-usernsexec", "-m", map1, "-m", map2, "-m",
- map3, "--", "chown", "0", path, NULL};
+ int hostuid = geteuid(), hostgid = getegid(), ret;
+ char map1[100], map2[100], map3[100], map4[100], map5[100], chown_arg[100];
+ char *args[] = { "lxc-usernsexec", "-m", map1, "-m", map2,
+ "-m", map3, "-m", map4, "-m", map5,
+ "--", "chown", chown_arg, path, NULL };
+ struct stat orig_stat;
+
+ // save original gid of "path"
+ if (stat(path, &orig_stat) < 0) {
+ ERROR("%s: failed to stat %s", __func__, path);
+ return -1;
+ }
- // "u:0:rootid:1"
- ret = snprintf(map1, 100, "u:0:%d:1", rootid);
+ // This is a trick for chgrp the file that is not owned by oneself.
+ if (chown(path, -1, hostgid) < 0) {
+ ERROR("Error chgrp %s", path);
+ return -1;
+ }
+
+ // "u:0:rootuid:1"
+ ret = snprintf(map1, 100, "u:0:%d:1", rootuid);
if (ret < 0 || ret >= 100) {
ERROR("Error uid printing map string");
return -1;
@@ -3568,10 +3588,31 @@ int chown_mapped_root(char *path, struct lxc_conf *conf)
return -1;
}
- // "g:0:hostgid:1"
- ret = snprintf(map3, 100, "g:0:%d:1", getgid());
+ // "g:0:rootgid:1"
+ ret = snprintf(map3, 100, "g:0:%d:1", rootgid);
if (ret < 0 || ret >= 100) {
- ERROR("Error uid printing map string");
+ ERROR("Error gid printing map string");
+ return -1;
+ }
+
+ // "g:hostgid:hostgid:1"
+ ret = snprintf(map4, 100, "g:%d:%d:1", hostgid, hostgid);
+ if (ret < 0 || ret >= 100) {
+ ERROR("Error gid printing map string");
+ return -1;
+ }
+
+ // "g:(orig_stat.st_gid):rootgid+(orig_stat.st_gid):1"
+ ret = snprintf(map5, 100, "g:%d:%d:1", orig_stat.st_gid, rootgid+orig_stat.st_gid);
+ if (ret < 0 || ret >= 100) {
+ ERROR("Error gid printing map string");
+ return -1;
+ }
+
+ // owner:group arg of chown
+ ret = snprintf(chown_arg, 100, "0:%d", orig_stat.st_gid);
+ if (ret < 0 || ret >= 100) {
+ ERROR("Error chown argument string");
return -1;
}
--
1.9.0
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