cls_cgroup: Fix oops when user send improperly 'tc filter add' request

I found a bug in cls_cgroup_change() in cls_cgroup.c.
cls_cgroup_change() expected tca[TCA_OPTIONS] was set from user space properly,
but tc in iproute2-2.6.29-1 (which I used) didn't set it.

In the current source code of tc in git, it set tca[TCA_OPTIONS].

  git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/iproute2.git

If we always use a newest iproute2 in git when we use cls_cgroup, 
we don't face this oops probably.
But I think, kernel shouldn't panic regardless of use program's behaviour. 

Signed-off-by: Minoru Usui <usui@mxm.nes.nec.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index cc29b44b1500..e5becb92b3e7 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -167,6 +167,9 @@ static int cls_cgroup_change(struct tcf_proto *tp, unsigned long base,
         struct tcf_exts e;
         int err;
 
+        if (!tca[TCA_OPTIONS])
+                return -EINVAL;
+
         if (head == NULL) {
                 if (!handle)
                         return -EINVAL;