From 0c3e0e3bb623c3735b8c9ab8aa8332f944f83a9f Mon Sep 17 00:00:00 2001
From: Kirill Tkhai <ktkhai@virtuozzo.com>
Date: Wed, 20 Mar 2019 12:16:42 +0300
Subject: [PATCH] tun: Add ioctl() TUNGETDEVNETNS cmd to allow obtaining real
net ns of tun device
In commit f2780d6d7475 "tun: Add ioctl() SIOCGSKNS cmd to allow
obtaining net ns of tun device" it was missed that tun may change
its net ns, while net ns of socket remains the same as it was
created initially. SIOCGSKNS returns net ns of socket, so it is
not suitable for obtaining net ns of device.
We may have two tun devices with the same names in two net ns,
and in this case it's not possible to determ, which of them
fd refers to (TUNGETIFF will return the same name).
This patch adds new ioctl() cmd for obtaining net ns of a device.
Reported-by: Harald Albrecht <harald.albrecht@gmx.net>
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
drivers/net/tun.c | 8 ++++++++
include/uapi/linux/if_tun.h | 1 +
2 files changed, 9 insertions(+)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index ef3b655149766..60d0a4e60ec5e 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -3102,6 +3102,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
tun_debug(KERN_INFO, tun, "tun_chr_ioctl cmd %u\n", cmd);
+ net = dev_net(tun->dev);
ret = 0;
switch (cmd) {
case TUNGETIFF:
@@ -3327,6 +3328,13 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
ret = tun_net_change_carrier(tun->dev, (bool)carrier);
break;
+ case TUNGETDEVNETNS:
+ ret = -EPERM;
+ if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+ goto unlock;
+ ret = open_related_ns(&net->ns, get_net_ns);
+ break;
+
default:
ret = -EINVAL;
break;
diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h
index 23a6753b37df3..454ae31b93c7a 100644
--- a/include/uapi/linux/if_tun.h
+++ b/include/uapi/linux/if_tun.h
@@ -60,6 +60,7 @@
#define TUNSETSTEERINGEBPF _IOR('T', 224, int)
#define TUNSETFILTEREBPF _IOR('T', 225, int)
#define TUNSETCARRIER _IOW('T', 226, int)
+#define TUNGETDEVNETNS _IO('T', 227)
/* TUNSETIFF ifr flags */
#define IFF_TUN 0x0001
--
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