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Merge branch 'tcp-robust-ooo'

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Eric Dumazet says:

====================
Juha-Matti Tilli reported that malicious peers could inject tiny
packets in out_of_order_queue, forcing very expensive calls
to tcp_collapse_ofo_queue() and tcp_prune_ofo_queue() for
every incoming packet.

With tcp_rmem[2] default of 6MB, the ooo queue could
contain ~7000 nodes.

This patch series makes sure we cut cpu cycles enough to
render the attack not critical.

We might in the future go further, like disconnecting
or black-holing proven malicious flows.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2018-07-23 12:01:36 -07:00
commit 1a4f14bab1
1 changed files with 50 additions and 12 deletions
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62
net/ipv4/tcp_input.c
View File

@ -4358,6 +4358,23 @@ static bool tcp_try_coalesce(struct sock *sk,
return true;
}
static bool tcp_ooo_try_coalesce(struct sock *sk,
struct sk_buff *to,
struct sk_buff *from,
bool *fragstolen)
{
bool res = tcp_try_coalesce(sk, to, from, fragstolen);
/* In case tcp_drop() is called later, update to->gso_segs */
if (res) {
u32 gso_segs = max_t(u16, 1, skb_shinfo(to)->gso_segs) +
max_t(u16, 1, skb_shinfo(from)->gso_segs);
skb_shinfo(to)->gso_segs = min_t(u32, gso_segs, 0xFFFF);
}
return res;
}
static void tcp_drop(struct sock *sk, struct sk_buff *skb)
{
sk_drops_add(sk, skb);
@ -4481,8 +4498,8 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
/* In the typical case, we are adding an skb to the end of the list.
* Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
*/
if (tcp_try_coalesce(sk, tp->ooo_last_skb,
skb, &fragstolen)) {
if (tcp_ooo_try_coalesce(sk, tp->ooo_last_skb,
skb, &fragstolen)) {
coalesce_done:
tcp_grow_window(sk, skb);
kfree_skb_partial(skb, fragstolen);
@ -4510,7 +4527,7 @@ coalesce_done:
/* All the bits are present. Drop. */
NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPOFOMERGE);
__kfree_skb(skb);
tcp_drop(sk, skb);
skb = NULL;
tcp_dsack_set(sk, seq, end_seq);
goto add_sack;
@ -4529,11 +4546,11 @@ coalesce_done:
TCP_SKB_CB(skb1)->end_seq);
NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPOFOMERGE);
__kfree_skb(skb1);
tcp_drop(sk, skb1);
goto merge_right;
}
} else if (tcp_try_coalesce(sk, skb1,
skb, &fragstolen)) {
} else if (tcp_ooo_try_coalesce(sk, skb1,
skb, &fragstolen)) {
goto coalesce_done;
}
p = &parent->rb_right;
@ -4902,6 +4919,7 @@ 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;
u32 start, end;
@ -4913,6 +4931,7 @@ new_range:
}
start = TCP_SKB_CB(skb)->seq;
end = TCP_SKB_CB(skb)->end_seq;
range_truesize = skb->truesize;
for (head = skb;;) {
skb = skb_rb_next(skb);
@ -4923,11 +4942,20 @@ 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))
@ -4942,6 +4970,7 @@ new_range:
* 2) not add too big latencies if thousands of packets sit there.
* (But if application shrinks SO_RCVBUF, we could still end up
* freeing whole queue here)
* 3) Drop at least 12.5 % of sk_rcvbuf to avoid malicious attacks.
*
* Return true if queue has shrunk.
*/
@ -4949,20 +4978,26 @@ static bool tcp_prune_ofo_queue(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
struct rb_node *node, *prev;
int goal;
if (RB_EMPTY_ROOT(&tp->out_of_order_queue))
return false;
NET_INC_STATS(sock_net(sk), LINUX_MIB_OFOPRUNED);
goal = sk->sk_rcvbuf >> 3;
node = &tp->ooo_last_skb->rbnode;
do {
prev = rb_prev(node);
rb_erase(node, &tp->out_of_order_queue);
goal -= rb_to_skb(node)->truesize;
tcp_drop(sk, rb_to_skb(node));
sk_mem_reclaim(sk);
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
!tcp_under_memory_pressure(sk))
break;
if (!prev || goal <= 0) {
sk_mem_reclaim(sk);
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
!tcp_under_memory_pressure(sk))
break;
goal = sk->sk_rcvbuf >> 3;
}
node = prev;
} while (node);
tp->ooo_last_skb = rb_to_skb(prev);
@ -4997,6 +5032,9 @@ static int tcp_prune_queue(struct sock *sk)
else if (tcp_under_memory_pressure(sk))
tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
return 0;
tcp_collapse_ofo_queue(sk);
if (!skb_queue_empty(&sk->sk_receive_queue))
tcp_collapse(sk, &sk->sk_receive_queue, NULL,