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Date: Thu, 10 Sep 2015 20:05:00 -0500
From: ebiederm@...ssion.com (Eric W. Biederman)
To: "Michael J. Coss" <michael.coss@...atel-lucent.com>
Cc: gregkh@...uxfoundation.org, davem@...emloft.net,
linux-kernel@...r.kernel.org, containers@...ts.linuxcontainers.org,
serge.hallyn@...ntu.com, stgraber@...ntu.com
Subject: Re: [PATCH 3/3] net/udevns: Netlink module to forward uevent to containers
"Michael J. Coss" <michael.coss@...atel-lucent.com> writes:
> New generic netlink module to provide an interface with the new
> forwarding interface for uevent. The driver allows a user to
> direct a uevent as read from the kernel to a specific network
> namespace by providing the uevent message, and a target process id.
> The uapi header file provides the message format.
If we can't just pass the message thourgh I don't expect genetlink is a
particularly good interface for this.
It would be nice if we could open some appropriate thing and the act of
getting a file descriptor ould suppress all of the uevent broadcast
messages in that network namespace.
Further GENL_ADMIN_PERM is an unfortunate choice for a permission check.
I don't see it as exploitable but I am not certain CAP_SYS_ADMIN is the
best capability to check. Beyond that we probably want to arrange
things so that we can use ns_capable so we can allow containers to hand
off their devices to child containers.
Implementations that do not allow for containers to nest bother me.
> Signed-off-by: Michael J. Coss <michael.coss@...atel-lucent.com>
> ---
> include/uapi/linux/Kbuild | 1 +
> include/uapi/linux/udevns.h | 19 ++++++++
> net/Kconfig | 1 +
> net/Makefile | 1 +
> net/udevns/Kconfig | 9 ++++
> net/udevns/Makefile | 5 ++
> net/udevns/udevns.c | 112 ++++++++++++++++++++++++++++++++++++++++++++
> net/udevns/udevns.h | 19 ++++++++
> 8 files changed, 167 insertions(+)
> create mode 100644 include/uapi/linux/udevns.h
> create mode 100644 net/udevns/Kconfig
> create mode 100644 net/udevns/Makefile
> create mode 100644 net/udevns/udevns.c
> create mode 100644 net/udevns/udevns.h
>
> diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
> index 1ff9942..9fb9c59 100644
> --- a/include/uapi/linux/Kbuild
> +++ b/include/uapi/linux/Kbuild
> @@ -404,6 +404,7 @@ header-y += toshiba.h
> header-y += tty_flags.h
> header-y += tty.h
> header-y += types.h
> +header-y += udevns.h
> header-y += udf_fs_i.h
> header-y += udp.h
> header-y += uhid.h
> diff --git a/include/uapi/linux/udevns.h b/include/uapi/linux/udevns.h
> new file mode 100644
> index 0000000..f5702f5
> --- /dev/null
> +++ b/include/uapi/linux/udevns.h
> @@ -0,0 +1,19 @@
> +#ifndef _UDEVNS_H_
> +#define _UDEVNS_H_
> +
> +enum udevns_msg_types {
> + UDEVNS_FORWARD_MSG = 0x1,
> + UDEVNS_CMD_MAX,
> +};
> +
> +enum udevns_attr {
> + UDEVNS_UNSPEC,
> + UDEVNS_PID,
> + UDEVNS_MSG,
> + __UDEVNS_ATTR_MAX,
> +};
> +
> +#define UDEVNS_ATTR_MAX (__UDEVNS_ATTR_MAX - 1)
> +#define UDEVNS_VERSION 0x1
> +
> +#endif
> diff --git a/net/Kconfig b/net/Kconfig
> index 57a7c5a..465e288 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -54,6 +54,7 @@ source "net/packet/Kconfig"
> source "net/unix/Kconfig"
> source "net/xfrm/Kconfig"
> source "net/iucv/Kconfig"
> +source "net/udevns/Kconfig"
>
> config INET
> bool "TCP/IP networking"
> diff --git a/net/Makefile b/net/Makefile
> index 3995613..bde7775 100644
> --- a/net/Makefile
> +++ b/net/Makefile
> @@ -74,3 +74,4 @@ obj-$(CONFIG_HSR) += hsr/
> ifneq ($(CONFIG_NET_SWITCHDEV),)
> obj-y += switchdev/
> endif
> +obj-$(CONFIG_UDEVNS) += udevns/
> diff --git a/net/udevns/Kconfig b/net/udevns/Kconfig
> new file mode 100644
> index 0000000..367e650
> --- /dev/null
> +++ b/net/udevns/Kconfig
> @@ -0,0 +1,9 @@
> +config UDEVNS
> + tristate "UDEV namespace bridge"
> + depends on SYSFS
> + default n
> + help
> + This option enables support for explicit forwarding of UDEV events to
> + other network namespaces
> +
> + If unsure, say N.
> diff --git a/net/udevns/Makefile b/net/udevns/Makefile
> new file mode 100644
> index 0000000..44c6b12
> --- /dev/null
> +++ b/net/udevns/Makefile
> @@ -0,0 +1,5 @@
> +#
> +# Makefile for the uevent namespace aware forwarder
> +#
> +#
> +obj-$(CONFIG_UDEVNS) += udevns.o
> diff --git a/net/udevns/udevns.c b/net/udevns/udevns.c
> new file mode 100644
> index 0000000..8b23751
> --- /dev/null
> +++ b/net/udevns/udevns.c
> @@ -0,0 +1,112 @@
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <net/sock.h>
> +#include <net/genetlink.h>
> +#include <linux/netlink.h>
> +#include <linux/skbuff.h>
> +#include <linux/fs.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +#include <linux/kobject.h>
> +#include <linux/sysfs.h>
> +
> +#include "udevns.h"
> +
> +#define DRIVER_AUTHOR "Michael J Coss <michael.coss@...atel-lucent.com>"
> +#define DRIVER_DESC "new udev namespace bridge"
> +#define DEVICE_NAME "udevns"
> +
> +#ifdef MODULE
> +#define UDEVNS_NAME (THIS_MODULE->name)
> +#else
> +#define UDEVNS_NAME "udevns"
> +#endif
> +
> +#define UDEVNS_INFO(fmt, args...) \
> + pr_info("[%s] " fmt, UDEVNS_NAME, ## args)
> +
> +#define UDEVNS_ERROR(fmt, args...) \
> + pr_err("[ERROR:%s:%s] " fmt, UDEVNS_NAME, __func__, ## args)
> +
> +#define UDEVNS_WARNING(fmt, args...) \
> + pr_warn("[WARNING:%s:%s] " fmt, UDEVNS_NAME, __func__, ## args)
> +
> +static struct genl_family udevns_genl_family = {
> + .id = GENL_ID_GENERATE,
> + .name = DEVICE_NAME,
> + .hdrsize = 0,
> + .version = UDEVNS_VERSION,
> + .maxattr = UDEVNS_ATTR_MAX,
> +};
> +
> +static const struct nla_policy udevns_fmsgpolicy[UDEVNS_ATTR_MAX + 1] = {
> + [UDEVNS_PID] = { .type = NLA_U32 },
> + [UDEVNS_MSG] = { .type = NLA_STRING, .len = UEVENT_BUFFER_SIZE},
> +};
> +
> +static int udevns_forwardmsg(struct sk_buff *skb, struct genl_info *info)
> +{
> + pid_t pid;
> + char *msg;
> + int msglen;
> + int err;
> +
> + if (!info->attrs[UDEVNS_PID]) {
> + UDEVNS_WARNING("missing PID from UDEVNS_FORWARD_MSG.\n");
> + return -EINVAL;
> + }
> +
> + if (!info->attrs[UDEVNS_MSG]) {
> + UDEVNS_WARNING("missing uevent from UDEVNS_FORWARD_MSG.\n");
> + return -EINVAL;
> + }
> +
> + pid = nla_get_u32(info->attrs[UDEVNS_PID]);
> + msg = nla_data(info->attrs[UDEVNS_MSG]);
> + msglen = nla_len(info->attrs[UDEVNS_MSG]);
> +
> + if (msglen < 0) {
> + UDEVNS_ERROR("Malformed uevent from UDEVNS_FORWARD_MSG.\n");
> + return -EINVAL;
> + }
> +
> + err = kobject_uevent_forward(msg, msglen, pid);
> + return err;
> +}
> +
> +static struct genl_ops udevns_genl_ops[] = {
> + {
> + .cmd = UDEVNS_FORWARD_MSG,
> + .flags = GENL_ADMIN_PERM,
> + .doit = udevns_forwardmsg,
> + .policy = udevns_fmsgpolicy,
> + },
> +};
> +
> +static int __init udevns_init(void)
> +{
> + int rc;
> +
> + UDEVNS_INFO("Starting udevns module\n");
> + rc = genl_register_family_with_ops(&udevns_genl_family,
> + udevns_genl_ops);
> + if (rc) {
> + UDEVNS_ERROR("Failed to register netlink interface\n");
> + return rc;
> + }
> + return 0;
> +}
> +
> +static void __exit udevns_exit(void)
> +{
> + UDEVNS_INFO("Exiting udevns module\n");
> + genl_unregister_family(&udevns_genl_family);
> +}
> +
> +module_init(udevns_init);
> +module_exit(udevns_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION(DRIVER_DESC);
> +MODULE_AUTHOR(DRIVER_AUTHOR);
> diff --git a/net/udevns/udevns.h b/net/udevns/udevns.h
> new file mode 100644
> index 0000000..f5702f5
> --- /dev/null
> +++ b/net/udevns/udevns.h
> @@ -0,0 +1,19 @@
> +#ifndef _UDEVNS_H_
> +#define _UDEVNS_H_
> +
> +enum udevns_msg_types {
> + UDEVNS_FORWARD_MSG = 0x1,
> + UDEVNS_CMD_MAX,
> +};
> +
> +enum udevns_attr {
> + UDEVNS_UNSPEC,
> + UDEVNS_PID,
> + UDEVNS_MSG,
> + __UDEVNS_ATTR_MAX,
> +};
> +
> +#define UDEVNS_ATTR_MAX (__UDEVNS_ATTR_MAX - 1)
> +#define UDEVNS_VERSION 0x1
> +
> +#endif
--
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