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[82.53.134.234]) by smtp.gmail.com with ESMTPSA id m24-20020aa7c2d8000000b0044dbecdcd29sm2914807edp.12.2022.10.31.01.43.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Oct 2022 01:43:31 -0700 (PDT) Date: Mon, 31 Oct 2022 09:43:27 +0100 From: Stefano Garzarella To: Dexuan Cui Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, arseny.krasnov@kaspersky.com, netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kys@microsoft.com, haiyangz@microsoft.com, stephen@networkplumber.org, wei.liu@kernel.org, linux-hyperv@vger.kernel.org Subject: Re: [PATCH 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data() Message-ID: <20221031084327.63vikvodhs7aowhe@sgarzare-redhat> References: <20221028205646.28084-1-decui@microsoft.com> <20221028205646.28084-3-decui@microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20221028205646.28084-3-decui@microsoft.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Oct 28, 2022 at 01:56:46PM -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 qeuue before checking s/qeuue/queue >vsock_connectible_has_data(). > >Fixes: b3f7fd54881b ("af_vsock: separate wait data loop") >Signed-off-by: Dexuan Cui >--- > 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); Since we are going to call again prepare_to_wait() on top of the loop, is finish_wait() call here really needed? What about following what we do in vsock_accept and vsock_connect? prepare_to_wait() while (condition) { ... prepare_to_wait(); } finish_wait() I find it a little more readable, but your solution is fine too. Thanks, Stefano