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[TCP]: Make sure write_queue_from does not begin with NULL ptr

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NULL ptr can be returned from tcp_write_queue_head to cached_skb
and then assigned to skb if packets_out was zero. Without this,
system is vulnerable to a carefully crafted ACKs which obviously
is remotely triggerable.

Besides, there's very little that needs to be done in sacktag
if there weren't any packets outstanding, just skipping the rest
doesn't hurt.

Signed-off-by: Ilpo Jrvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Jrvinen 2007-11-14 15:47:18 -08:00 committed by David S. Miller
parent fb93134dfc
commit 96a2d41a3e
1 changed files with 5 additions and 0 deletions
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5
net/ipv4/tcp_input.c
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@ -1269,6 +1269,9 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
return 0;
if (!tp->packets_out)
goto out;
/* SACK fastpath:
* if the only SACK change is the increase of the end_seq of
* the first block then only apply that SACK block
@ -1515,6 +1518,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
(!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
tcp_update_reordering(sk, tp->fackets_out - reord, 0);
out:
#if FASTRETRANS_DEBUG > 0
BUG_TRAP((int)tp->sacked_out >= 0);
BUG_TRAP((int)tp->lost_out >= 0);