From: Michael Tokarev Date: Tue, 3 Feb 2009 07:34:56 +0000 (-0800) Subject: tun: Check supplemental groups in TUN/TAP driver. X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1bded710a574f20d41bc9e7fb531301db282d623;p=linux-beck.git 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 Signed-off-by: David S. Miller --- diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 457f2d7430cf..15d67635bb10 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -123,7 +123,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file) /* Check permissions */ if (((tun->owner != -1 && cred->euid != tun->owner) || - (tun->group != -1 && cred->egid != tun->group)) && + (tun->group != -1 && !in_egroup_p(tun->group))) && !capable(CAP_NET_ADMIN)) return -EPERM;