From: Ilpo Järvinen Date: Wed, 14 Nov 2007 23:47:18 +0000 (-0800) Subject: [TCP]: Make sure write_queue_from does not begin with NULL ptr X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=96a2d41a3e495734b63bff4e5dd0112741b93b38;p=deliverable%2Flinux.git [TCP]: Make sure write_queue_from does not begin with NULL ptr 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 --- 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);