Commit 32b2f4b1 authored Jul 17, 2015 by Daniel Borkmann Committed by David S. Miller Jul 21, 2015

sched: cls_flow: fix panic on filter replace

The following test case causes a NULL pointer dereference in cls_flow:

tc filter add dev foo parent 1: handle 0x1 flow hash keys dst action ok
tc filter replace dev foo parent 1: pref 49152 handle 0x1 \
flow hash keys mark action drop

To be more precise, actually two different panics are fixed, the first
occurs because tcf_exts_init() is not called on the newly allocated
filter when we do a replace. And the second panic uncovered after that
happens since the arguments of list_replace_rcu() are swapped, the old
element needs to be the first argument and the new element the second.

Fixes: 70da9f0b ("net: sched: cls_flow use RCU")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent ff3532f2

net/sched/cls_flow.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -425,6 +425,8 @@ static int flow_change(struct net net, struct sk_buff in_skb,
		if (!fnew)
		goto err2;

		tcf_exts_init(&fnew->exts, TCA_FLOW_ACT, TCA_FLOW_POLICE);

		fold = (struct flow_filter )arg;
		if (fold) {
		err = -EINVAL;
		@@ -486,7 +488,6 @@ static int flow_change(struct net net, struct sk_buff in_skb,
		fnew->mask = ~0U;
		fnew->tp = tp;
		get_random_bytes(&fnew->hashrnd, 4);
		tcf_exts_init(&fnew->exts, TCA_FLOW_ACT, TCA_FLOW_POLICE);
		}

		fnew->perturb_timer.function = flow_perturbation;
		@@ -526,7 +527,7 @@ static int flow_change(struct net net, struct sk_buff in_skb,
		if (*arg == 0)
		list_add_tail_rcu(&fnew->list, &head->filters);
		else
		list_replace_rcu(&fnew->list, &fold->list);
		list_replace_rcu(&fold->list, &fnew->list);

		*arg = (unsigned long)fnew;