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sched: cls_flow: fix panic on filter replace

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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: 70da9f0bf9 ("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>
This commit is contained in:
Daniel Borkmann 2015-07-17 22:38:45 +02:00 committed by David S. Miller
parent ff3532f265
commit 32b2f4b196
1 changed files with 3 additions and 2 deletions
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5
net/sched/cls_flow.c
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@ -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;