Code: static int net_ctl_permissions(struct ctl_table_header *head,
			       struct ctl_table *table)
{
	struct net *net = container_of(head->set, struct net, sysctls);
	kuid_t root_uid = make_kuid(net->user_ns, 0);
	kgid_t root_gid = make_kgid(net->user_ns, 0);
 
 	/* Allow network administrator to have same access as root. */
 	if (ns_capable(net->user_ns, CAP_NET_ADMIN) ||
	    uid_eq(root_uid, current_uid())) {
 		int mode = (table->mode >> 6) & 7;
 		return (mode << 6) | (mode << 3) | mode;
 	}
 	/* Allow netns root group to have the same access as the root group */
	if (gid_eq(root_gid, current_gid())) {
 		int mode = (table->mode >> 3) & 7;
 		return (mode << 3) | mode;
 	}
	return table->mode;
}

Vulnerability Type: Bypass 
CWE ID: CWE-20
Summary: The net_ctl_permissions function in net/sysctl_net.c in the Linux kernel before 3.11.5 does not properly determine uid and gid values, which allows local users to bypass intended /proc/sys/net restrictions via a crafted application.
Commit Message: net: Update the sysctl permissions handler to test effective uid/gid

Modify the code to use current_euid(), and in_egroup_p, as in done
in fs/proc/proc_sysctl.c:test_perm()

Cc: stable@vger.kernel.org
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reported-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>