From b738a185beaab8728943acdb3e67371b8a88185e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 19 Mar 2020 12:49:55 -0700 Subject: tcp: ensure skb->dev is NULL before leaving TCP stack skb->rbnode is sharing three skb fields : next, prev, dev When a packet is sent, TCP keeps the original skb (master) in a rtx queue, which was converted to rbtree a while back. __tcp_transmit_skb() is responsible to clone the master skb, and add the TCP header to the clone before sending it to network layer. skb_clone() already clears skb->next and skb->prev, but copies the master oskb->dev into the clone. We need to clear skb->dev, otherwise lower layers could interpret the value as a pointer to a netdev. This old bug surfaced recently when commit 28f8bfd1ac94 ("netfilter: Support iif matches in POSTROUTING") was merged. Before this netfilter commit, skb->dev value was ignored and changed before reaching dev_queue_xmit() Fixes: 75c119afe14f ("tcp: implement rb-tree based retransmit queue") Fixes: 28f8bfd1ac94 ("netfilter: Support iif matches in POSTROUTING") Signed-off-by: Eric Dumazet Reported-by: Martin Zaharinov Cc: Florian Westphal Cc: Pablo Neira Ayuso Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'net/ipv4/tcp_output.c') diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 306e25d743e8..e8cf8fde3d37 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1109,6 +1109,10 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, if (unlikely(!skb)) return -ENOBUFS; + /* retransmit skbs might have a non zero value in skb->dev + * because skb->dev is aliased with skb->rbnode.rb_left + */ + skb->dev = NULL; } inet = inet_sk(sk); -- cgit v1.2.3