[3/4] SUNRPC: Don't call connect() more than once on a TCP socket

From: Trond Myklebust <trond.myklebust@hammerspace.com>

commit 89f42494f92f448747bd8a7ab1ae8b5d5520577d upstream.

Avoid socket state races due to repeated calls to ->connect() using the
same socket. If connect() returns 0 due to the connection having
completed, but we are in fact in a closing state, then we may leave the
XPRT_CONNECTING flag set on the transport.

Reported-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Fixes: 3be232f11a3c ("SUNRPC: Prevent immediate close+reconnect")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
[meenashanmugam: Backported to 5.10: Fixed merge conflict in xs_tcp_setup_socket]
Signed-off-by: Meena Shanmugam <meenashanmugam@google.com>
---
 include/linux/sunrpc/xprtsock.h |  1 +
 net/sunrpc/xprtsock.c           | 21 +++++++++++----------
 2 files changed, 12 insertions(+), 10 deletions(-)

On Sat, May 14, 2022 at 05:34:52AM +0000, Meena Shanmugam wrote:
> From: Trond Myklebust <trond.myklebust@hammerspace.com>
> 
> commit 89f42494f92f448747bd8a7ab1ae8b5d5520577d upstream.
> 
> Avoid socket state races due to repeated calls to ->connect() using the
> same socket. If connect() returns 0 due to the connection having
> completed, but we are in fact in a closing state, then we may leave the
> XPRT_CONNECTING flag set on the transport.
> 
> Reported-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
> Fixes: 3be232f11a3c ("SUNRPC: Prevent immediate close+reconnect")
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> [meenashanmugam: Backported to 5.10: Fixed merge conflict in xs_tcp_setup_socket]
> Signed-off-by: Meena Shanmugam <meenashanmugam@google.com>
> ---
>  include/linux/sunrpc/xprtsock.h |  1 +
>  net/sunrpc/xprtsock.c           | 21 +++++++++++----------
>  2 files changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/sunrpc/xprtsock.h b/include/linux/sunrpc/xprtsock.h
> index 8c2a712cb242..689062afdd61 100644
> --- a/include/linux/sunrpc/xprtsock.h
> +++ b/include/linux/sunrpc/xprtsock.h
> @@ -89,5 +89,6 @@ struct sock_xprt {
>  #define XPRT_SOCK_WAKE_WRITE	(5)
>  #define XPRT_SOCK_WAKE_PENDING	(6)
>  #define XPRT_SOCK_WAKE_DISCONNECT	(7)
> +#define XPRT_SOCK_CONNECT_SENT	(8)
>  
>  #endif /* _LINUX_SUNRPC_XPRTSOCK_H */
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index 60c58eb9a456..33a81f9703b1 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -2260,10 +2260,14 @@ static void xs_tcp_setup_socket(struct work_struct *work)
>  	struct rpc_xprt *xprt = &transport->xprt;
>  	int status = -EIO;
>  
> -	if (!sock) {
> -		sock = xs_create_sock(xprt, transport,
> -				xs_addr(xprt)->sa_family, SOCK_STREAM,
> -				IPPROTO_TCP, true);
> +	if (xprt_connected(xprt))
> +		goto out;
> +	if (test_and_clear_bit(XPRT_SOCK_CONNECT_SENT,
> +			       &transport->sock_state) ||
> +	    !sock) {
> +		xs_reset_transport(transport);
> +		sock = xs_create_sock(xprt, transport, xs_addr(xprt)->sa_family,
> +				      SOCK_STREAM, IPPROTO_TCP, true);
>  		if (IS_ERR(sock)) {
>  			status = PTR_ERR(sock);
>  			goto out;
> @@ -2294,6 +2298,7 @@ static void xs_tcp_setup_socket(struct work_struct *work)
>  		break;
>  	case 0:
>  	case -EINPROGRESS:
> +		set_bit(XPRT_SOCK_CONNECT_SENT, &transport->sock_state);
>  	case -EALREADY:
>  		xprt_unlock_connect(xprt, transport);
>  		return;
> @@ -2345,13 +2350,9 @@ static void xs_connect(struct rpc_xprt *xprt, struct rpc_task *task)
>  
>  	WARN_ON_ONCE(!xprt_lock_connect(xprt, task, transport));
>  
> -	if (transport->sock != NULL && !xprt_connecting(xprt)) {
> +	if (transport->sock != NULL) {
>  		dprintk("RPC:       xs_connect delayed xprt %p for %lu "
> -				"seconds\n",
> -				xprt, xprt->reestablish_timeout / HZ);
> -
> -		/* Start by resetting any existing state */
> -		xs_reset_transport(transport);
> +			"seconds\n", xprt, xprt->reestablish_timeout / HZ);
>  
>  		delay = xprt_reconnect_delay(xprt);
>  		xprt_reconnect_backoff(xprt, XS_TCP_INIT_REEST_TO);
> -- 
> 2.36.0.550.gb090851708-goog
> 

This commit added a build warning.  Always properly test your changes,
they can not add warnings.

I've fixed it up by hand now.

thanks,

greg k-h

On Mon, May 16, 2022 at 2:34 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> This commit added a build warning.  Always properly test your changes,
> they can not add warnings.
>
> I've fixed it up by hand now.
>
> thanks,
>
> greg k-h

Sorry about that. Thank you for fixing it.

Thanks,
Meena