linux-kernel - [PATCH 5.13 514/800] skmsg: Clear skb redirect pointer before dropping it

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Date:   Mon, 12 Jul 2021 08:08:57 +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, Jiang Wang <jiang.wang@...edance.com>,
        Cong Wang <cong.wang@...edance.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.13 514/800] skmsg: Clear skb redirect pointer before dropping it

From: Cong Wang <cong.wang@...edance.com>

[ Upstream commit 30b9c54a707db4155735cf71f4600241c1b7b6ff ]

When we drop skb inside sk_psock_skb_redirect(), we have to clear
its skb->_sk_redir pointer too, otherwise kfree_skb() would
misinterpret it as a valid skb->_skb_refdst and dst_release()
would eventually complain.

Fixes: e3526bb92a20 ("skmsg: Move sk_redir from TCP_SKB_CB to skb")
Reported-by: Jiang Wang <jiang.wang@...edance.com>
Signed-off-by: Cong Wang <cong.wang@...edance.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: John Fastabend <john.fastabend@...il.com>
Acked-by: Jakub Sitnicki <jakub@...udflare.com>
Link: https://lore.kernel.org/bpf/20210615021342.7416-5-xiyou.wangcong@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/core/skmsg.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 43ce17a6a585..df545748cd6a 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -866,12 +866,14 @@ static void sk_psock_skb_redirect(struct sk_buff *skb)
 	 * a socket that is in this state so we drop the skb.
 	 */
 	if (!psock_other || sock_flag(sk_other, SOCK_DEAD)) {
+		skb_bpf_redirect_clear(skb);
 		kfree_skb(skb);
 		return;
 	}
 	spin_lock_bh(&psock_other->ingress_lock);
 	if (!sk_psock_test_state(psock_other, SK_PSOCK_TX_ENABLED)) {
 		spin_unlock_bh(&psock_other->ingress_lock);
+		skb_bpf_redirect_clear(skb);
 		kfree_skb(skb);
 		return;
 	}
-- 
2.30.2