Subject: Re: [PATCH net v2] bpf, sockmap: fix the sk->sk_forward_alloc warning of sk_stream_kill_queues()

From: Jakub Sitnicki <[email-masked]>
Date: Mon, 31 Oct 2022 18:56:49 +0100

On Sat, Oct 29, 2022 at 07:44 AM +08, Wang Yufen wrote:
> 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 <[email-masked]>
> Signed-off-by: Wang Yufen <[email-masked]>
> Acked-by: John Fastabend <[email-masked]>
> ---
> v1 -> v2: typo fixup
>  net/ipv4/tcp_bpf.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> index a1626af..774d481 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, sent, 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);
> +		sent = orgsize - msg->sg.size;

If I'm reading the code right, it's the same as:

                sent = tosend - msg->sg.size;

If so, no need for orgsize.

>  
>  		if (eval == __SK_REDIRECT)
>  			sock_put(sk_redir);
> @@ -375,7 +377,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
>  		    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);
> +				sk_mem_charge(sk, tosend - sent);
>  			goto more_data;
>  		}
>  	}