netdev - Re: [PATCH v2 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait

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Date:   Wed, 2 Nov 2022 10:31:37 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, arseny.krasnov@...persky.com,
        netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kys@...rosoft.com,
        haiyangz@...rosoft.com, stephen@...workplumber.org,
        wei.liu@...nel.org, linux-hyperv@...r.kernel.org
Subject: Re: [PATCH v2 2/2] vsock: fix possible infinite sleep in
 vsock_connectible_wait_data()

On Mon, Oct 31, 2022 at 07:17:06PM -0700, Dexuan Cui wrote:
>Currently vsock_connectible_has_data() may miss a wakeup operation
>between vsock_connectible_has_data() == 0 and the prepare_to_wait().
>
>Fix the race by adding the process to the wait queue before checking
>vsock_connectible_has_data().
>
>Fixes: b3f7fd54881b ("af_vsock: separate wait data loop")
>Signed-off-by: Dexuan Cui <decui@...rosoft.com>
>---
>
>Changes in v2 (Thanks Stefano!):
>  Fixed a typo in the commit message.
>  Removed the unnecessary finish_wait() at the end of the loop.

LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

>
> net/vmw_vsock/af_vsock.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index d258fd43092e..884eca7f6743 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1905,8 +1905,11 @@ static int vsock_connectible_wait_data(struct sock *sk,
> 	err = 0;
> 	transport = vsk->transport;
>
>-	while ((data = vsock_connectible_has_data(vsk)) == 0) {
>+	while (1) {
> 		prepare_to_wait(sk_sleep(sk), wait, TASK_INTERRUPTIBLE);
>+		data = vsock_connectible_has_data(vsk);
>+		if (data != 0)
>+			break;
>
> 		if (sk->sk_err != 0 ||
> 		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
>-- 
>2.25.1
>