[PATCH v3 14/30] inet: frags: do not clone skb in ip_expire()
From: Stephen Hemminger <stephen@networkplumber.org>
Date: 2018-09-13 14:58:46
Also in:
stable
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
From: Eric Dumazet <edumazet@google.com>
An skb_clone() was added in commit ec4fbd64751d ("inet: frag: release
spinlock before calling icmp_send()")
While fixing the bug at that time, it also added a very high cost
for DDOS frags, as the ICMP rate limit is applied after this
expensive operation (skb_clone() + consume_skb(), implying memory
allocations, copy, and freeing)
We can use skb_get(head) here, all we want is to make sure skb wont
be freed by another cpu.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 1eec5d5670084ee644597bd26c25e22c69b9f748)
---
net/ipv4/ip_fragment.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index dc3ed0ac4c58..88fa8ffc5558 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c@@ -143,8 +143,8 @@ static bool frag_expire_skip_icmp(u32 user) static void ip_expire(struct timer_list *t) { struct inet_frag_queue *frag = from_timer(frag, t, timer); - struct sk_buff *clone, *head; const struct iphdr *iph; + struct sk_buff *head; struct net *net; struct ipq *qp; int err;
@@ -187,16 +187,12 @@ static void ip_expire(struct timer_list *t) (skb_rtable(head)->rt_type != RTN_LOCAL)) goto out; - clone = skb_clone(head, GFP_ATOMIC); + skb_get(head); + spin_unlock(&qp->q.lock); + icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); + kfree_skb(head); + goto out_rcu_unlock; - /* Send an ICMP "Fragment Reassembly Timeout" message. */ - if (clone) { - spin_unlock(&qp->q.lock); - icmp_send(clone, ICMP_TIME_EXCEEDED, - ICMP_EXC_FRAGTIME, 0); - consume_skb(clone); - goto out_rcu_unlock; - } out: spin_unlock(&qp->q.lock); out_rcu_unlock:
--
2.18.0