netdev - [PATCH net] tcp: also NULL skb->dev when copy was needed

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Message-Id: <20200320155202.25719-1-fw@strlen.de>
Date:   Fri, 20 Mar 2020 16:52:02 +0100
From:   Florian Westphal <fw@...len.de>
To:     <netdev@...r.kernel.org>
Cc:     Florian Westphal <fw@...len.de>, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] tcp: also NULL skb->dev when copy was needed

In rare cases retransmit logic will make a full skb copy, which will not
trigger the zeroing added in recent change
b738a185beaa ("tcp: ensure skb->dev is NULL before leaving TCP stack").

Cc: Eric Dumazet <edumazet@...gle.com>
Fixes: 75c119afe14f ("tcp: implement rb-tree based retransmit queue")
Fixes: 28f8bfd1ac94 ("netfilter: Support iif matches in POSTROUTING")
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/ipv4/tcp_output.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e8cf8fde3d37..2f45cde168c4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3041,8 +3041,12 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 
 		tcp_skb_tsorted_save(skb) {
 			nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
-			err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
-				     -ENOBUFS;
+			if (nskb) {
+				nskb->dev = NULL;
+				err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
+			} else {
+				err = -ENOBUFS;
+			}
 		} tcp_skb_tsorted_restore(skb);
 
 		if (!err) {
-- 
2.24.1