netdev - [PATCH net] bpf, sockmap: fix the sk->sk_forward_alloc warning of sk_stream_kill

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Date:   Fri, 28 Oct 2022 15:22:34 +0800
From:   Wang Yufen <wangyufen@...wei.com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     <john.fastabend@...il.com>, <jakub@...udflare.com>
Subject: [PATCH net] bpf, sockmap: fix the sk->sk_forward_alloc warning of sk_stream_kill_queues()

When running `test_sockmap` selftests, got the following warning:

WARNING: CPU: 2 PID: 197 at net/core/stream.c:205 sk_stream_kill_queues+0xd3/0xf0
Call Trace:
  <TASK>
  inet_csk_destroy_sock+0x55/0x110
  tcp_rcv_state_process+0xd28/0x1380
  ? tcp_v4_do_rcv+0x77/0x2c0
  tcp_v4_do_rcv+0x77/0x2c0
  __release_sock+0x106/0x130
  __tcp_close+0x1a7/0x4e0
  tcp_close+0x20/0x70
  inet_release+0x3c/0x80
  __sock_release+0x3a/0xb0
  sock_close+0x14/0x20
  __fput+0xa3/0x260
  task_work_run+0x59/0xb0
  exit_to_user_mode_prepare+0x1b3/0x1c0
  syscall_exit_to_user_mode+0x19/0x50
  do_syscall_64+0x48/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae

The root case is: In commit 84472b436e76 ("bpf, sockmap: Fix more
uncharged while msg has more_data") , I used msg->sg.size replace
tosend rudely, which break the
   if (msg->apply_bytes && msg->apply_bytes < send)
scene.

Fixes: 84472b436e76 ("bpf, sockmap: Fix more uncharged while msg has more_data")
Reported-by: Jakub Sitnicki <jakub@...udflare.com>
Signed-off-by: Wang Yufen <wangyufen@...wei.com>
---
 net/ipv4/tcp_bpf.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index a1626af..38d4735 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -278,7 +278,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
 {
 	bool cork = false, enospc = sk_msg_full(msg);
 	struct sock *sk_redir;
-	u32 tosend, delta = 0;
+	u32 tosend, orgsize, sended, delta = 0;
 	u32 eval = __SK_NONE;
 	int ret;

@@ -333,10 +333,12 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
 			cork = true;
 			psock->cork = NULL;
 		}
-		sk_msg_return(sk, msg, msg->sg.size);
+		sk_msg_return(sk, msg, tosend);
 		release_sock(sk);

+		orgsize = msg->sg.size;
 		ret = tcp_bpf_sendmsg_redir(sk_redir, msg, tosend, flags);
+		sended = orgsize - msg->sg.size;

 		if (eval == __SK_REDIRECT)
 			sock_put(sk_redir);
@@ -374,8 +376,8 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
 		if (msg &&
 		    msg->sg.data[msg->sg.start].page_link &&
 		    msg->sg.data[msg->sg.start].length) {
-			if (eval == __SK_REDIRECT)
-				sk_mem_charge(sk, msg->sg.size);
+			if (eval == __SK_REDIRECT && tosend > sended)
+				sk_mem_charge(sk, tosend - sended);
 			goto more_data;
 		}
 	}
-- 
1.8.3.1