linux-kernel - [PATCH 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait

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Message-Id: <20221028205646.28084-3-decui@microsoft.com>
Date:   Fri, 28 Oct 2022 13:56:46 -0700
From:   Dexuan Cui <decui@...rosoft.com>
To:     sgarzare@...hat.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, arseny.krasnov@...persky.com,
        netdev@...r.kernel.org
Cc:     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,
        Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()

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 qeuue before checking
vsock_connectible_has_data().

Fixes: b3f7fd54881b ("af_vsock: separate wait data loop")
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
 net/vmw_vsock/af_vsock.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index d258fd43092e..03a6b5bc6ba7 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) ||
@@ -1937,6 +1940,8 @@ static int vsock_connectible_wait_data(struct sock *sk,
 			err = -EAGAIN;
 			break;
 		}
+
+		finish_wait(sk_sleep(sk), wait);
 	}
 
 	finish_wait(sk_sleep(sk), wait);
-- 
2.25.1