From: Jiri Pirko <jpirko@redhat.com>
Date: Wed, 20 May 2009 17:11:06 +0200
Subject: [net] tun: allow group ownership of TUN/TAP devices
Message-id: 20090520151106.GI5299@psychotron.englab.brq.redhat.com
O-Subject: [RHEL5.5 patch] BZ497955 net: tun: Allow group ownership of TUN/TAP devices.
Bugzilla: 497955
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>
RH-Acked-by: David Miller <davem@redhat.com>
RH-Acked-by: Jiri Olsa <jolsa@redhat.com>

BZ497955
https://bugzilla.redhat.com/show_bug.cgi?id=497955

Description:
Introduce a new syscall TUNSETGROUP for group ownership setting of tap
devices. The user now is allowed to send packages if either his euid or
his egid matches the one specified via tunctl (via -u or -g
respecitvely). If both, gid and uid, are set via tunctl, both have to
match.

Upstream:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8c644623fe7e41f59fe97cdf666cba3cb7ced7d8

Brew:
https://brewweb.devel.redhat.com/taskinfo?taskID=1807439

Test:
Booted and tested on x86_64.

Jirka

Signed-off-by: Jiri Pirko <jpirko@redhat.com>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 785ef15..c73f5cf 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -600,6 +600,7 @@ static void tun_setup(struct net_device *dev)
 	init_waitqueue_head(&tun->read_wait);
 
 	tun->owner = -1;
+	tun->group = -1;
 
 	SET_MODULE_OWNER(dev);
 	dev->open = tun_net_open;
@@ -664,8 +665,11 @@ static int tun_set_iff(struct file *file, struct ifreq *ifr)
 			return -EBUSY;
 
 		/* Check permissions */
-		if (tun->owner != -1 &&
-		    current->euid != tun->owner && !capable(CAP_NET_ADMIN))
+		if (((tun->owner != -1 &&
+		      current->euid != tun->owner) ||
+		     (tun->group != -1 &&
+		      current->egid != tun->group)) &&
+		     !capable(CAP_NET_ADMIN))
 			return -EPERM;
 	} 
 	else if (__dev_get_by_name(ifr->ifr_name)) 
@@ -920,6 +924,13 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file,
 		DBG(KERN_INFO "%s: owner set to %d\n", tun->dev->name, tun->owner);
 		break;
 
+	case TUNSETGROUP:
+		/* Set group of the device */
+		tun->group= (gid_t) arg;
+
+		DBG(KERN_INFO "%s: group set to %d\n", tun->dev->name, tun->group);
+		break;
+
 	case TUNSETLINK:
 		/* Only allow setting the type when the interface is down */
 		if (tun->dev->flags & IFF_UP) {
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
index 25660dd..f6a73cd 100644
--- a/include/linux/if_tun.h
+++ b/include/linux/if_tun.h
@@ -38,6 +38,7 @@ struct tun_struct {
 	unsigned long 		flags;
 	int			attached;
 	uid_t			owner;
+	gid_t			group;
 
 	wait_queue_head_t	read_wait;
 	struct sk_buff_head	readq;
@@ -84,6 +85,7 @@ struct tun_struct {
 #define TUNSETPERSIST _IOW('T', 203, int) 
 #define TUNSETOWNER   _IOW('T', 204, int)
 #define TUNSETLINK    _IOW('T', 205, int)
+#define TUNSETGROUP   _IOW('T', 206, int)
 #define TUNGETFEATURES _IOR('T', 207, unsigned int)
 #define TUNSETOFFLOAD _IOW('T', 208, unsigned int)
 #define TUNGETIFF      _IOR('T', 210, unsigned int)