[PATCH 5.4 035/155] tcp: also NULL skb->dev when copy was needed

Greg Kroah-Hartman
2020-03-31T09:12:12Z

From: Florian Westphal <fw@strlen.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@google.com>
Fixes: 75c119afe14f ("tcp: implement rb-tree based retransmit queue")
Fixes: 28f8bfd1ac94 ("netfilter: Support iif matches in POSTROUTING")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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) {