netdev - [PATCH net-next] tcp: cleanup sk_tx_skb

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Message-Id: <20190329194617.195528-1-edumazet@google.com>
Date:   Fri, 29 Mar 2019 12:46:17 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH net-next] tcp: cleanup sk_tx_skb_cache before reuse

TCP stack relies on the fact that a freshly allocated skb
has skb->cb[] and skb_shinfo(skb)->tx_flags cleared.

When recycling tx skb, we must ensure these fields are cleared.

Fixes: 472c2e07eef0 ("tcp: add one skb cache for tx")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Soheil Hassas Yeganeh <soheil@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
---
 net/ipv4/tcp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 82bd707c03472f2cebb1a90d5f1c13acc821468f..603e770d59b3db96adca9602319d2f6970a56285 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -872,6 +872,8 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
 			sk->sk_tx_skb_cache = NULL;
 			pskb_trim(skb, 0);
 			INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
+			skb_shinfo(skb)->tx_flags = 0;
+			memset(TCP_SKB_CB(skb), 0, sizeof(struct tcp_skb_cb));
 			return skb;
 		}
 	}
-- 
2.21.0.392.gf8f6787159e-goog