I think libudev is a solution to a completely different problem. It is
possible I am blind but I just don't see how libudev even attempts to
solve the problem.
The desire is to plop a distro install into a subdirectory. Fire up a
container around it, and let the distro's userspace do it's thing to
manage hotplug events.
devtmpfs can be faked fairly easily.
I don't know about sysfs.
Sending events that say you have hotplugged is the largest practical
problem.
On the minimal side I think the patch below is enough to let us fake up
uevents for the container and make things work. I have heard the words
faking uevents and is a bad thing. But I have not heard a reason or seen
any attempt at explanation. My guess is that we are simply talking
about different problems.
I would like to see someone wire up all of the userspace bits and see
how well hotplug can be made to work before I walk down the path
represented by this patch but it seems reasonable. But I do have
anecdotal reports from someone who walked a similar path that this is
enough to bring up a full desktop system in a container.
Eric
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 7a6c396a263b..46d05783da82 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -38,6 +38,7 @@ extern void netlink_table_ungrab(void);
#define NL_CFG_F_NONROOT_RECV (1 << 0)
#define NL_CFG_F_NONROOT_SEND (1 << 1)
+#define NL_CFG_F_IMPERSONATE_KERN (1 << 2)
/* optional Netlink kernel configuration parameters */
struct netlink_kernel_cfg {
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 52e5abbc41db..f75e34397df8 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -375,9 +375,12 @@ static int uevent_net_init(struct net *net)
struct uevent_sock *ue_sk;
struct netlink_kernel_cfg cfg = {
.groups = 1,
- .flags = NL_CFG_F_NONROOT_RECV,
+ .flags = NL_CFG_F_NONROOT_RECV | NL_CFG_F_IMPERSONATE_KERN,
};
+ if (net->user_ns != &init_user_ns)
+ return 0;
+
ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
if (!ue_sk)
return -ENOMEM;
@@ -399,6 +402,9 @@ static void uevent_net_exit(struct net *net)
{
struct uevent_sock *ue_sk;
+ if (net->user_ns != &init_user_ns)
+ return;
+
mutex_lock(&uevent_sock_mutex);
list_for_each_entry(ue_sk, &uevent_sock_list, list) {
if (sock_net(ue_sk->sk) == net)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 0c61b59175dc..71863cc465eb 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1252,7 +1252,7 @@ static int netlink_release(struct socket *sock)
skb_queue_purge(&sk->sk_write_queue);
- if (nlk->portid) {
+ if (sk_hashed(sk)) {
struct netlink_notify n = {
.net = sock_net(sk),
.protocol = sk->sk_protocol,
@@ -1409,11 +1409,21 @@ static int netlink_bind(struct socket *sock, struct
sockaddr *addr,
return err;
}
- if (nlk->portid) {
+ if (sk_hashed(sk)) {
if (nladdr->nl_pid != nlk->portid)
return -EINVAL;
} else {
- err = nladdr->nl_pid ?
+ bool autobind = nladdr->nl_pid == 0;
+ if (nladdr->nl_pid == 0 && (nladdr->nl_pad == 0xffff)) {
+ if (!(nl_table[sk->sk_protocol].flags &
NL_CFG_F_IMPERSONATE_KERN))
+ return -EPERM;
+ if (net->user_ns == &init_user_ns)
+ return -EPERM;
+ if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+ return -EPERM;
+ autobind = false;
+ }
+ err = !autobind ?
netlink_insert(sk, net, nladdr->nl_pid) :
netlink_autobind(sock);
if (err)
@@ -1467,7 +1477,7 @@ static int netlink_connect(struct socket *sock, struct
sockaddr *addr,
if (nladdr->nl_groups && !netlink_capable(sock, NL_CFG_F_NONROOT_SEND))
return -EPERM;
- if (!nlk->portid)
+ if (!sk_hashed(sk))
err = netlink_autobind(sock);
if (err == 0) {
@@ -2228,7 +2238,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct
socket *sock,
dst_group = nlk->dst_group;
}
- if (!nlk->portid) {
+ if (!sk_hashed(sk)) {
err = netlink_autobind(sock);
if (err)
goto out;
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