Date: Tue, 10 Oct 2023 08:50:00 -0700 (PDT)
From: Mat Martineau <martineau@...nel.org>
To: Paolo Abeni <pabeni@...hat.com>
cc: netdev@...r.kernel.org, Ayush Sawal <ayush.sawal@...lsio.com>, 
    "David S. Miller" <davem@...emloft.net>, 
    Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
    David Ahern <dsahern@...nel.org>, mptcp@...ts.linux.dev, 
    Boris Pismenny <borisp@...dia.com>, Tom Deseyn <tdeseyn@...hat.com>
Subject: Re: [PATCH net] tcp: allow again tcp_disconnect() when threads are
 waiting

On Mon, 9 Oct 2023, Paolo Abeni wrote:

> As reported by Tom, .NET and applications build on top of it rely
> on connect(AF_UNSPEC) to async cancel pending I/O operations on TCP
> socket.
>
> The blamed commit below caused a regression, as such cancellation
> can now fail.
>
> As suggested by Eric, this change addresses the problem explicitly
> causing blocking I/O operation to terminate immediately (with an error)
> when a concurrent disconnect() is executed.
>
> Instead of tracking the number of threads blocked on a given socket,
> track the number of disconnect() issued on such socket. If such counter
> changes after a blocking operation releasing and re-acquiring the socket
> lock, error out the current operation.
>
> Fixes: 4faeee0cf8a5 ("tcp: deny tcp_disconnect() when threads are waiting")
> Reported-by: Tom Deseyn <tdeseyn@...hat.com>
> Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1886305
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

For MPTCP changes:

Acked-by: Mat Martineau <martineau@...nel.org>


> ---
> .../chelsio/inline_crypto/chtls/chtls_io.c    | 35 +++++++++++++++----
> include/net/sock.h                            | 10 +++---
> net/core/stream.c                             | 12 ++++---
> net/ipv4/af_inet.c                            |  8 +++--
> net/ipv4/inet_connection_sock.c               |  1 -
> net/ipv4/tcp.c                                | 17 ++++-----
> net/ipv4/tcp_bpf.c                            |  4 +++
> net/mptcp/protocol.c                          |  8 +----
> net/tls/tls_main.c                            | 10 ++++--
> net/tls/tls_sw.c                              | 19 ++++++----
> 10 files changed, 79 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_io.c b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_io.c
> index 5fc64e47568a..caa1eaed190d 100644
> --- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_io.c
> +++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_io.c
> @@ -911,7 +911,7 @@ static int csk_wait_memory(struct chtls_dev *cdev,
> 			   struct sock *sk, long *timeo_p)
> {
> 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
> -	int err = 0;
> +	int ret, err = 0;
> 	long current_timeo;
> 	long vm_wait = 0;
> 	bool noblock;
> @@ -942,10 +942,13 @@ static int csk_wait_memory(struct chtls_dev *cdev,
>
> 		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
> 		sk->sk_write_pending++;
> -		sk_wait_event(sk, &current_timeo, sk->sk_err ||
> -			      (sk->sk_shutdown & SEND_SHUTDOWN) ||
> -			      (csk_mem_free(cdev, sk) && !vm_wait), &wait);
> +		ret = sk_wait_event(sk, &current_timeo, sk->sk_err ||
> +				    (sk->sk_shutdown & SEND_SHUTDOWN) ||
> +				    (csk_mem_free(cdev, sk) && !vm_wait),
> +				    &wait);
> 		sk->sk_write_pending--;
> +		if (ret < 0)
> +			goto do_error;
>
> 		if (vm_wait) {
> 			vm_wait -= current_timeo;
> @@ -1348,6 +1351,7 @@ static int chtls_pt_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> 	int copied = 0;
> 	int target;
> 	long timeo;
> +	int ret;
>
> 	buffers_freed = 0;
>
> @@ -1423,7 +1427,11 @@ static int chtls_pt_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> 		if (copied >= target)
> 			break;
> 		chtls_cleanup_rbuf(sk, copied);
> -		sk_wait_data(sk, &timeo, NULL);
> +		ret = sk_wait_data(sk, &timeo, NULL);
> +		if (ret < 0) {
> +			copied = copied ? : ret;
> +			goto unlock;
> +		}
> 		continue;
> found_ok_skb:
> 		if (!skb->len) {
> @@ -1518,6 +1526,8 @@ static int chtls_pt_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
>
> 	if (buffers_freed)
> 		chtls_cleanup_rbuf(sk, copied);
> +
> +unlock:
> 	release_sock(sk);
> 	return copied;
> }
> @@ -1534,6 +1544,7 @@ static int peekmsg(struct sock *sk, struct msghdr *msg,
> 	int copied = 0;
> 	size_t avail;          /* amount of available data in current skb */
> 	long timeo;
> +	int ret;
>
> 	lock_sock(sk);
> 	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
> @@ -1585,7 +1596,11 @@ static int peekmsg(struct sock *sk, struct msghdr *msg,
> 			release_sock(sk);
> 			lock_sock(sk);
> 		} else {
> -			sk_wait_data(sk, &timeo, NULL);
> +			ret = sk_wait_data(sk, &timeo, NULL);
> +			if (ret < 0) {
> +				copied = ret;
> +				break;
> +			}
> 		}
>
> 		if (unlikely(peek_seq != tp->copied_seq)) {
> @@ -1656,6 +1671,7 @@ int chtls_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> 	int copied = 0;
> 	long timeo;
> 	int target;             /* Read at least this many bytes */
> +	int ret;
>
> 	buffers_freed = 0;
>
> @@ -1747,7 +1763,11 @@ int chtls_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> 		if (copied >= target)
> 			break;
> 		chtls_cleanup_rbuf(sk, copied);
> -		sk_wait_data(sk, &timeo, NULL);
> +		ret = sk_wait_data(sk, &timeo, NULL);
> +		if (ret < 0) {
> +			copied = copied ? : ret;
> +			goto unlock;
> +		}
> 		continue;
>
> found_ok_skb:
> @@ -1816,6 +1836,7 @@ int chtls_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> 	if (buffers_freed)
> 		chtls_cleanup_rbuf(sk, copied);
>
> +unlock:
> 	release_sock(sk);
> 	return copied;
> }
> diff --git a/include/net/sock.h b/include/net/sock.h
> index b770261fbdaf..92f7ea62a915 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -336,7 +336,7 @@ struct sk_filter;
>   *	@sk_cgrp_data: cgroup data for this cgroup
>   *	@sk_memcg: this socket's memory cgroup association
>   *	@sk_write_pending: a write to stream socket waits to start
> -  *	@sk_wait_pending: number of threads blocked on this socket
> +  *	@sk_disconnects: number of disconnect operations performed on this sock
>   *	@sk_state_change: callback to indicate change in the state of the sock
>   *	@sk_data_ready: callback to indicate there is data to be processed
>   *	@sk_write_space: callback to indicate there is bf sending space available
> @@ -429,7 +429,7 @@ struct sock {
> 	unsigned int		sk_napi_id;
> #endif
> 	int			sk_rcvbuf;
> -	int			sk_wait_pending;
> +	int			sk_disconnects;
>
> 	struct sk_filter __rcu	*sk_filter;
> 	union {
> @@ -1189,8 +1189,7 @@ static inline void sock_rps_reset_rxhash(struct sock *sk)
> }
>
> #define sk_wait_event(__sk, __timeo, __condition, __wait)		\
> -	({	int __rc;						\
> -		__sk->sk_wait_pending++;				\
> +	({	int __rc, __dis = __sk->sk_disconnects;			\
> 		release_sock(__sk);					\
> 		__rc = __condition;					\
> 		if (!__rc) {						\
> @@ -1200,8 +1199,7 @@ static inline void sock_rps_reset_rxhash(struct sock *sk)
> 		}							\
> 		sched_annotate_sleep();					\
> 		lock_sock(__sk);					\
> -		__sk->sk_wait_pending--;				\
> -		__rc = __condition;					\
> +		__rc = __dis == __sk->sk_disconnects ? __condition : -EPIPE; \
> 		__rc;							\
> 	})
>
> diff --git a/net/core/stream.c b/net/core/stream.c
> index f5c4e47df165..96fbcb9bbb30 100644
> --- a/net/core/stream.c
> +++ b/net/core/stream.c
> @@ -117,7 +117,7 @@ EXPORT_SYMBOL(sk_stream_wait_close);
>  */
> int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
> {
> -	int err = 0;
> +	int ret, err = 0;
> 	long vm_wait = 0;
> 	long current_timeo = *timeo_p;
> 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
> @@ -142,11 +142,13 @@ int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
>
> 		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
> 		sk->sk_write_pending++;
> -		sk_wait_event(sk, &current_timeo, READ_ONCE(sk->sk_err) ||
> -						  (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) ||
> -						  (sk_stream_memory_free(sk) &&
> -						  !vm_wait), &wait);
> +		ret = sk_wait_event(sk, &current_timeo, READ_ONCE(sk->sk_err) ||
> +				    (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) ||
> +				    (sk_stream_memory_free(sk) && !vm_wait),
> +				    &wait);
> 		sk->sk_write_pending--;
> +		if (ret < 0)
> +			goto do_error;
>
> 		if (vm_wait) {
> 			vm_wait -= current_timeo;
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index 3d2e30e20473..a7aa082f9a4c 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -597,7 +597,6 @@ static long inet_wait_for_connect(struct sock *sk, long timeo, int writebias)
>
> 	add_wait_queue(sk_sleep(sk), &wait);
> 	sk->sk_write_pending += writebias;
> -	sk->sk_wait_pending++;
>
> 	/* Basic assumption: if someone sets sk->sk_err, he _must_
> 	 * change state of the socket from TCP_SYN_*.
> @@ -613,7 +612,6 @@ static long inet_wait_for_connect(struct sock *sk, long timeo, int writebias)
> 	}
> 	remove_wait_queue(sk_sleep(sk), &wait);
> 	sk->sk_write_pending -= writebias;
> -	sk->sk_wait_pending--;
> 	return timeo;
> }
>
> @@ -696,6 +694,7 @@ int __inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
> 		int writebias = (sk->sk_protocol == IPPROTO_TCP) &&
> 				tcp_sk(sk)->fastopen_req &&
> 				tcp_sk(sk)->fastopen_req->data ? 1 : 0;
> +		int dis = sk->sk_disconnects;
>
> 		/* Error code is set above */
> 		if (!timeo || !inet_wait_for_connect(sk, timeo, writebias))
> @@ -704,6 +703,11 @@ int __inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
> 		err = sock_intr_errno(timeo);
> 		if (signal_pending(current))
> 			goto out;
> +
> +		if (dis != sk->sk_disconnects) {
> +			err = -EPIPE;
> +			goto out;
> +		}
> 	}
>
> 	/* Connection was closed by RST, timeout, ICMP error
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index aeebe8816689..394a498c2823 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -1145,7 +1145,6 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
> 	if (newsk) {
> 		struct inet_connection_sock *newicsk = inet_csk(newsk);
>
> -		newsk->sk_wait_pending = 0;
> 		inet_sk_set_state(newsk, TCP_SYN_RECV);
> 		newicsk->icsk_bind_hash = NULL;
> 		newicsk->icsk_bind2_hash = NULL;
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 3f66cdeef7de..368f0d16c817 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -831,7 +831,9 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
> 			 */
> 			if (!skb_queue_empty(&sk->sk_receive_queue))
> 				break;
> -			sk_wait_data(sk, &timeo, NULL);
> +			ret = sk_wait_data(sk, &timeo, NULL);
> +			if (ret < 0)
> +				break;
> 			if (signal_pending(current)) {
> 				ret = sock_intr_errno(timeo);
> 				break;
> @@ -2442,7 +2444,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
> 			__sk_flush_backlog(sk);
> 		} else {
> 			tcp_cleanup_rbuf(sk, copied);
> -			sk_wait_data(sk, &timeo, last);
> +			err = sk_wait_data(sk, &timeo, last);
> +			if (err < 0) {
> +				err = copied ? : err;
> +				goto out;
> +			}
> 		}
>
> 		if ((flags & MSG_PEEK) &&
> @@ -2966,12 +2972,6 @@ int tcp_disconnect(struct sock *sk, int flags)
> 	int old_state = sk->sk_state;
> 	u32 seq;
>
> -	/* Deny disconnect if other threads are blocked in sk_wait_event()
> -	 * or inet_wait_for_connect().
> -	 */
> -	if (sk->sk_wait_pending)
> -		return -EBUSY;
> -
> 	if (old_state != TCP_CLOSE)
> 		tcp_set_state(sk, TCP_CLOSE);
>
> @@ -3092,6 +3092,7 @@ int tcp_disconnect(struct sock *sk, int flags)
> 		sk->sk_frag.offset = 0;
> 	}
> 	sk_error_report(sk);
> +	sk->sk_disconnects++;
> 	return 0;
> }
> EXPORT_SYMBOL(tcp_disconnect);
> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> index 327268203001..ba2e92188124 100644
> --- a/net/ipv4/tcp_bpf.c
> +++ b/net/ipv4/tcp_bpf.c
> @@ -307,6 +307,8 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk,
> 		}
>
> 		data = tcp_msg_wait_data(sk, psock, timeo);
> +		if (data < 0)
> +			return data;
> 		if (data && !sk_psock_queue_empty(psock))
> 			goto msg_bytes_ready;
> 		copied = -EAGAIN;
> @@ -351,6 +353,8 @@ static int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
>
> 		timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
> 		data = tcp_msg_wait_data(sk, psock, timeo);
> +		if (data < 0)
> +			return data;
> 		if (data) {
> 			if (!sk_psock_queue_empty(psock))
> 				goto msg_bytes_ready;
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index e252539b1e19..22dd27cce4e6 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -3098,12 +3098,6 @@ static int mptcp_disconnect(struct sock *sk, int flags)
> {
> 	struct mptcp_sock *msk = mptcp_sk(sk);
>
> -	/* Deny disconnect if other threads are blocked in sk_wait_event()
> -	 * or inet_wait_for_connect().
> -	 */
> -	if (sk->sk_wait_pending)
> -		return -EBUSY;
> -
> 	/* We are on the fastopen error path. We can't call straight into the
> 	 * subflows cleanup code due to lock nesting (we are already under
> 	 * msk->firstsocket lock).
> @@ -3144,6 +3138,7 @@ static int mptcp_disconnect(struct sock *sk, int flags)
>
> 	WRITE_ONCE(sk->sk_shutdown, 0);
> 	sk_error_report(sk);
> +	sk->sk_disconnects++;
> 	return 0;
> }
>
> @@ -3173,7 +3168,6 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
> 		inet_sk(nsk)->pinet6 = mptcp_inet6_sk(nsk);
> #endif
>
> -	nsk->sk_wait_pending = 0;
> 	__mptcp_init_sock(nsk);
>
> 	msk = mptcp_sk(nsk);
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index 02f583ff9239..002483e60c19 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -139,8 +139,8 @@ void update_sk_prot(struct sock *sk, struct tls_context *ctx)
>
> int wait_on_pending_writer(struct sock *sk, long *timeo)
> {
> -	int rc = 0;
> 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
> +	int ret, rc = 0;
>
> 	add_wait_queue(sk_sleep(sk), &wait);
> 	while (1) {
> @@ -154,9 +154,13 @@ int wait_on_pending_writer(struct sock *sk, long *timeo)
> 			break;
> 		}
>
> -		if (sk_wait_event(sk, timeo,
> -				  !READ_ONCE(sk->sk_write_pending), &wait))
> +		ret = sk_wait_event(sk, timeo,
> +				    !READ_ONCE(sk->sk_write_pending), &wait);
> +		if (ret) {
> +			if (ret < 0)
> +				rc = ret;
> 			break;
> +		}
> 	}
> 	remove_wait_queue(sk_sleep(sk), &wait);
> 	return rc;
> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
> index d1fc295b83b5..e9d1e83a859d 100644
> --- a/net/tls/tls_sw.c
> +++ b/net/tls/tls_sw.c
> @@ -1291,6 +1291,7 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
> 	struct tls_context *tls_ctx = tls_get_ctx(sk);
> 	struct tls_sw_context_rx *ctx = tls_sw_ctx_rx(tls_ctx);
> 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
> +	int ret = 0;
> 	long timeo;
>
> 	timeo = sock_rcvtimeo(sk, nonblock);
> @@ -1302,6 +1303,9 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
> 		if (sk->sk_err)
> 			return sock_error(sk);
>
> +		if (ret < 0)
> +			return ret;
> +
> 		if (!skb_queue_empty(&sk->sk_receive_queue)) {
> 			tls_strp_check_rcv(&ctx->strp);
> 			if (tls_strp_msg_ready(ctx))
> @@ -1320,10 +1324,10 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
> 		released = true;
> 		add_wait_queue(sk_sleep(sk), &wait);
> 		sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
> -		sk_wait_event(sk, &timeo,
> -			      tls_strp_msg_ready(ctx) ||
> -			      !sk_psock_queue_empty(psock),
> -			      &wait);
> +		ret = sk_wait_event(sk, &timeo,
> +				    tls_strp_msg_ready(ctx) ||
> +				    !sk_psock_queue_empty(psock),
> +				    &wait);
> 		sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
> 		remove_wait_queue(sk_sleep(sk), &wait);
>
> @@ -1852,6 +1856,7 @@ static int tls_rx_reader_acquire(struct sock *sk, struct tls_sw_context_rx *ctx,
> 				 bool nonblock)
> {
> 	long timeo;
> +	int ret;
>
> 	timeo = sock_rcvtimeo(sk, nonblock);
>
> @@ -1861,14 +1866,16 @@ static int tls_rx_reader_acquire(struct sock *sk, struct tls_sw_context_rx *ctx,
> 		ctx->reader_contended = 1;
>
> 		add_wait_queue(&ctx->wq, &wait);
> -		sk_wait_event(sk, &timeo,
> -			      !READ_ONCE(ctx->reader_present), &wait);
> +		ret = sk_wait_event(sk, &timeo,
> +				    !READ_ONCE(ctx->reader_present), &wait);
> 		remove_wait_queue(&ctx->wq, &wait);
>
> 		if (timeo <= 0)
> 			return -EAGAIN;
> 		if (signal_pending(current))
> 			return sock_intr_errno(timeo);
> +		if (ret < 0)
> +			return ret;
> 	}
>
> 	WRITE_ONCE(ctx->reader_present, 1);
> -- 
> 2.41.0
>
>
>

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