linux-kernel - [PATCH 5.5 036/170] tcp: also NULL skb->dev when copy was needed

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Message-Id: <20200331085427.868028952@linuxfoundation.org>
Date:   Tue, 31 Mar 2020 10:57:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.5 036/170] tcp: also NULL skb->dev when copy was needed

From: Florian Westphal <fw@...len.de>

[ Upstream commit 07f8e4d0fddbf2f87e4cefb551278abc38db8cdd ]

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>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp_output.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2976,8 +2976,12 @@ int __tcp_retransmit_skb(struct sock *sk
 
 		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) {