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| author | Eric Dumazet <edumazet@google.com> | 2018-03-31 12:58:54 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-03-31 23:25:39 -0400 |
| commit | 1eec5d5670084ee644597bd26c25e22c69b9f748 (patch) | |
| tree | 2b665adfd16baae97a8caa9426db3d168935a385 /net/ipv4/ip_fragment.c | |
| parent | 3e67f106f619dcfaf6f4e2039599bdb69848c714 (diff) | |
| download | lwn-1eec5d5670084ee644597bd26c25e22c69b9f748.tar.gz lwn-1eec5d5670084ee644597bd26c25e22c69b9f748.zip | |
inet: frags: do not clone skb in ip_expire()
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>
Diffstat (limited to 'net/ipv4/ip_fragment.c')
| -rw-r--r-- | net/ipv4/ip_fragment.c | 16 |
1 files changed, 6 insertions, 10 deletions
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 053869f2c49b..fb185d9a5cc7 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: |