From 32b2f4b196b37695fdb42b31afcbc15399d6ef91 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 17 Jul 2015 22:38:45 +0200 Subject: [PATCH] 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: 70da9f0bf999 ("net: sched: cls_flow use RCU") Signed-off-by: Daniel Borkmann Acked-by: John Fastabend Signed-off-by: David S. Miller --- net/sched/cls_flow.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/sched/cls_flow.c b/net/sched/cls_flow.c index 76bc3a20ffdb..bb2a0f529c1f 100644 --- a/net/sched/cls_flow.c +++ b/net/sched/cls_flow.c @@ -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;