From: Danny Feng <dfeng@redhat.com>
Date: Thu, 3 Dec 2009 09:50:09 -0500
Subject: [net] tun: check supplemental groups in TUN/TAP driver
Message-id: <20091203094945.8192.67128.sendpatchset@dhcp-65-180.nay.redhat.com>
Patchwork-id: 21663
O-Subject: [PATCH RHEL5.5] tun: Check supplemental groups in TUN/TAP driver
Bugzilla: 540786
RH-Acked-by: Dean Nelson <dnelson@redhat.com>
RH-Acked-by: Jarod Wilson <jarod@redhat.com>

backport of upstream commit 1bded71:

    tun: Check supplemental groups in TUN/TAP driver.

    Michael Tokarev wrote:
    []
    > 2, and this is the main one: How about supplementary groups?
    >
    > Here I have a valid usage case: a group of testers running various
    > versions of windows using KVM (kernel virtual machine), 1 at a time,
    > to test some software.  kvm is set up to use bridge with a tap device
    > (there should be a way to connect to the machine).  Anyone on that group
    > has to be able to start/stop the virtual machines.
    >
    > My first attempt - pretty obvious when I saw -g option of tunctl - is
    > to add group ownership for the tun device and add a supplementary group
    > to each user (their primary group should be different).  But that fails,
    > since kernel only checks for egid, not any other group ids.
    >
    > What's the reasoning to not allow supplementary groups and to only check
    > for egid?

    Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
    Signed-off-by: David S. Miller <davem@davemloft.net>

brew build:
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=2120272

resolves bz#540786

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 8dd6048..4df9ef0 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -668,7 +668,7 @@ static int tun_set_iff(struct file *file, struct ifreq *ifr)
 		if (((tun->owner != -1 &&
 		      current->euid != tun->owner) ||
 		     (tun->group != -1 &&
-		      current->egid != tun->group)) &&
+		      !in_egroup_p(tun->group))) &&
 		     !capable(CAP_NET_ADMIN))
 			return -EPERM;
 	}