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tun: Add ioctl() SIOCGSKNS cmd to allow obtaining net ns of tun device

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This patch adds possibility to get tun device's net namespace fd
in the same way we allow to do that for sockets.

Socket ioctl numbers do not intersect with tun-specific, and there
is already SIOCSIFHWADDR used in tun code. So, SIOCGSKNS number
is choosen instead of custom-made for this functionality.

Note, that open_related_ns() uses plain get_net_ns() and it's safe
(net can't be already dead at this moment):

  tun socket is allocated via sk_alloc() with zero last arg (kern = 0).
  So, each alive socket increments net::count, and the socket is definitely
  alive during ioctl syscall.

Also, common variable net is introduced, so small cleanup in TUNSETIFF
is made.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kirill Tkhai 2018-02-14 16:40:14 +03:00 committed by David S. Miller
parent 24dce0800b
commit f2780d6d74
1 changed files with 14 additions and 2 deletions
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16
drivers/net/tun.c
View File

@ -78,6 +78,7 @@
#include <linux/mutex.h>
#include <linux/uaccess.h>
#include <linux/proc_fs.h>
/* Uncomment to enable debugging */
/* #define TUN_DEBUG 1 */
@ -2793,6 +2794,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
struct tun_struct *tun;
void __user* argp = (void __user*)arg;
struct ifreq ifr;
struct net *net;
kuid_t owner;
kgid_t group;
int sndbuf;
@ -2801,7 +2803,8 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
int le;
int ret;
if (cmd == TUNSETIFF || cmd == TUNSETQUEUE || _IOC_TYPE(cmd) == SOCK_IOC_TYPE) {
if (cmd == TUNSETIFF || cmd == TUNSETQUEUE ||
(_IOC_TYPE(cmd) == SOCK_IOC_TYPE && cmd != SIOCGSKNS)) {
if (copy_from_user(&ifr, argp, ifreq_len))
return -EFAULT;
} else {
@ -2821,6 +2824,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
rtnl_lock();
tun = tun_get(tfile);
net = sock_net(&tfile->sk);
if (cmd == TUNSETIFF) {
ret = -EEXIST;
if (tun)
@ -2828,7 +2832,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
ifr.ifr_name[IFNAMSIZ-1] = '\0';
ret = tun_set_iff(sock_net(&tfile->sk), file, &ifr);
ret = tun_set_iff(net, file, &ifr);
if (ret)
goto unlock;
@ -2850,6 +2854,14 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
tfile->ifindex = ifindex;
goto unlock;
}
if (cmd == SIOCGSKNS) {
ret = -EPERM;
if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
goto unlock;
ret = open_related_ns(&net->ns, get_net_ns);
goto unlock;
}
ret = -EBADFD;
if (!tun)