Commit 32b2f4b1 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller

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: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJohn Fastabend <john.r.fastabend@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ff3532f2
...@@ -425,6 +425,8 @@ static int flow_change(struct net *net, struct sk_buff *in_skb, ...@@ -425,6 +425,8 @@ static int flow_change(struct net *net, struct sk_buff *in_skb,
if (!fnew) if (!fnew)
goto err2; goto err2;
tcf_exts_init(&fnew->exts, TCA_FLOW_ACT, TCA_FLOW_POLICE);
fold = (struct flow_filter *)*arg; fold = (struct flow_filter *)*arg;
if (fold) { if (fold) {
err = -EINVAL; err = -EINVAL;
...@@ -486,7 +488,6 @@ static int flow_change(struct net *net, struct sk_buff *in_skb, ...@@ -486,7 +488,6 @@ static int flow_change(struct net *net, struct sk_buff *in_skb,
fnew->mask = ~0U; fnew->mask = ~0U;
fnew->tp = tp; fnew->tp = tp;
get_random_bytes(&fnew->hashrnd, 4); get_random_bytes(&fnew->hashrnd, 4);
tcf_exts_init(&fnew->exts, TCA_FLOW_ACT, TCA_FLOW_POLICE);
} }
fnew->perturb_timer.function = flow_perturbation; fnew->perturb_timer.function = flow_perturbation;
...@@ -526,7 +527,7 @@ static int flow_change(struct net *net, struct sk_buff *in_skb, ...@@ -526,7 +527,7 @@ static int flow_change(struct net *net, struct sk_buff *in_skb,
if (*arg == 0) if (*arg == 0)
list_add_tail_rcu(&fnew->list, &head->filters); list_add_tail_rcu(&fnew->list, &head->filters);
else else
list_replace_rcu(&fnew->list, &fold->list); list_replace_rcu(&fold->list, &fnew->list);
*arg = (unsigned long)fnew; *arg = (unsigned long)fnew;
......
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