From 96a2d41a3e495734b63bff4e5dd0112741b93b38 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ilpo=20J=E4rvinen?= Date: Wed, 14 Nov 2007 15:47:18 -0800 Subject: [PATCH] [TCP]: Make sure write_queue_from does not begin with NULL ptr MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Järvinen Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 12ae9a68cdaa..3f126ece8eb5 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -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); -- 2.30.2