netdev - [PATCH net-next 4/4] bpf, sockmap: Fix double uncharge the mem of sk

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Date:   Mon, 21 Feb 2022 18:31:05 +0800
From:   Wang Yufen <wangyufen@...wei.com>
To:     <john.fastabend@...il.com>, <daniel@...earbox.net>,
        <jakub@...udflare.com>, <lmb@...udflare.com>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>,
        <yoshfuji@...ux-ipv6.org>, <dsahern@...nel.org>, <kuba@...nel.org>,
        <ast@...nel.org>, <andrii@...nel.org>, <kafai@...com>,
        <songliubraving@...com>, <yhs@...com>, <kpsingh@...nel.org>,
        <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        Wang Yufen <wangyufen@...wei.com>
Subject: [PATCH net-next 4/4] bpf, sockmap: Fix double uncharge the mem of sk_msg

If tcp_bpf_sendmsg is running during a tear down operation, psock may be
freed.

tcp_bpf_sendmsg()
 tcp_bpf_send_verdict()
  sk_msg_return()
  tcp_bpf_sendmsg_redir()
   unlikely(!psock))
   sk_msg_free()

The mem of msg has been uncharged in tcp_bpf_send_verdict() by
sk_msg_return(), so we need to use sk_msg_free_nocharge while psock
is null.

This issue can cause the following info:
WARNING: CPU: 0 PID: 2136 at net/ipv4/af_inet.c:155 inet_sock_destruct+0x13c/0x260
Call Trace:
 <TASK>
 __sk_destruct+0x24/0x1f0
 sk_psock_destroy+0x19b/0x1c0
 process_one_work+0x1b3/0x3c0
 worker_thread+0x30/0x350
 ? process_one_work+0x3c0/0x3c0
 kthread+0xe6/0x110
 ? kthread_complete_and_exit+0x20/0x20
 ret_from_fork+0x22/0x30
 </TASK>

Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Wang Yufen <wangyufen@...wei.com>
---
 net/ipv4/tcp_bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 1f0364e06619..03c037d2a055 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -139,7 +139,7 @@ int tcp_bpf_sendmsg_redir(struct sock *sk, struct sk_msg *msg,
 	int ret;

 	if (unlikely(!psock)) {
-		sk_msg_free(sk, msg);
+		sk_msg_free_nocharge(sk, msg);
 		return 0;
 	}
 	ret = ingress ? bpf_tcp_ingress(sk, psock, msg, bytes, flags) :
-- 
2.25.1