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tcp: detect malicious patterns in tcp_collapse_ofo_queue()

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[ Upstream commit 3d4bf93ac1 ]

In case an attacker feeds tiny packets completely out of order,
tcp_collapse_ofo_queue() might scan the whole rb-tree, performing
expensive copies, but not changing socket memory usage at all.

1) Do not attempt to collapse tiny skbs.
2) Add logic to exit early when too many tiny skbs are detected.

We prefer not doing aggressive collapsing (which copies packets)
for pathological flows, and revert to tcp_prune_ofo_queue() which
will be less expensive.

In the future, we might add the possibility of terminating flows
that are proven to be malicious.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet
2018-07-23 09:28:19 -07:00
committed by Greg Kroah-Hartman
parent 81e6b01d1c
commit 6285a74a53
1 changed files with 13 additions and 2 deletions
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15
net/ipv4/tcp_input.c
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@@ -4877,6 +4877,7 @@ end:
static void tcp_collapse_ofo_queue(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
u32 range_truesize, sum_tiny = 0;
struct sk_buff *skb, *head;
struct rb_node *p;
u32 start, end;
@@ -4895,6 +4896,7 @@ new_range:
}
start = TCP_SKB_CB(skb)->seq;
end = TCP_SKB_CB(skb)->end_seq;
range_truesize = skb->truesize;
for (head = skb;;) {
skb = tcp_skb_next(skb, NULL);
@@ -4905,11 +4907,20 @@ new_range:
if (!skb ||
after(TCP_SKB_CB(skb)->seq, end) ||
before(TCP_SKB_CB(skb)->end_seq, start)) {
tcp_collapse(sk, NULL, &tp->out_of_order_queue,
head, skb, start, end);
/* Do not attempt collapsing tiny skbs */
if (range_truesize != head->truesize ||
end - start >= SKB_WITH_OVERHEAD(SK_MEM_QUANTUM)) {
tcp_collapse(sk, NULL, &tp->out_of_order_queue,
head, skb, start, end);
} else {
sum_tiny += range_truesize;
if (sum_tiny > sk->sk_rcvbuf >> 3)
return;
}
goto new_range;
}
range_truesize += skb->truesize;
if (unlikely(before(TCP_SKB_CB(skb)->seq, start)))
start = TCP_SKB_CB(skb)->seq;
if (after(TCP_SKB_CB(skb)->end_seq, end))