[PATCH v2 0/2] vsock: remove an unused variable and fix infinite sleep

Patch 1 removes the unused 'wait' variable.
Patch 2 fixes an infinite sleep issue reported by a hv_sock user.

Made v2 to address Stefano's comments.
Please see each patch's header for changes in v2.

Dexuan Cui (2):
  vsock: remove the unused 'wait' in vsock_connectible_recvmsg()
  vsock: fix possible infinite sleep in vsock_connectible_wait_data()

 net/vmw_vsock/af_vsock.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

-- 
2.25.1

Remove the unused variable introduced by 19c1b90e1979.

Fixes: 19c1b90e1979 ("af_vsock: separate receive data loop")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
---

Changes in v2:
  Added Stefano's Reviewed-by.

 net/vmw_vsock/af_vsock.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index ee418701cdee..d258fd43092e 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c

@@ -2092,8 +2092,6 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	const struct vsock_transport *transport;
 	int err;
 
-	DEFINE_WAIT(wait);
-
 	sk = sock->sk;
 	vsk = vsock_sk(sk);
 	err = 0;

-- 
2.25.1

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@microsoft.com>
---

Changes in v2 (Thanks Stefano!):
  Fixed a typo in the commit message.
  Removed the unnecessary finish_wait() at the end of the loop.

 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

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@microsoft.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@redhat.com>

On Wed, Nov 02, 2022 at 10:31:37AM +0100, Stefano Garzarella wrote:

On Mon, Oct 31, 2022 at 07:17:06PM -0700, Dexuan Cui wrote:

quoted

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@microsoft.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@redhat.com>

And I would add

Reported-by: Frédéric Dalleau <redacted>

Since Frédéric posted a similar patch some months ago (I lost it because 
netdev and I were not in cc):
https://lore.kernel.org/virtualization/20220824074251.2336997-2-frederic.dalleau@docker.com/

Thanks,
Stefano

Hi Dexuan, Stefano,

Tested-by: Frédéric Dalleau <redacted>

Regards,
Frédéric


On Wed, Nov 2, 2022 at 10:42 AM Stefano Garzarella [off-list ref] wrote:

On Wed, Nov 02, 2022 at 10:31:37AM +0100, Stefano Garzarella wrote:

quoted

On Mon, Oct 31, 2022 at 07:17:06PM -0700, Dexuan Cui wrote:

quoted

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@microsoft.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@redhat.com>

And I would add

Reported-by: Frédéric Dalleau <redacted>

Since Frédéric posted a similar patch some months ago (I lost it because
netdev and I were not in cc):
https://lore.kernel.org/virtualization/20220824074251.2336997-2-frederic.dalleau@docker.com/

Thanks,
Stefano

From: Frederic Dalleau <redacted>
Sent: Wednesday, November 2, 2022 6:31 AM
To: Stefano Garzarella <sgarzare@redhat.com>
...
Hi Dexuan, Stefano,

Tested-by: Frédéric Dalleau <redacted>

Regards,
Frédéric

Thank you, Frederic! I didn't realize you posted a similar patch in Aug :-)

Thanks Stefano for reviewing!

Thanks,
-- Dexuan

Hello:

This series was applied to netdev/net.git (master)
by Paolo Abeni [off-list ref]:

On Mon, 31 Oct 2022 19:17:04 -0700 you wrote:

Patch 1 removes the unused 'wait' variable.
Patch 2 fixes an infinite sleep issue reported by a hv_sock user.

Made v2 to address Stefano's comments.
Please see each patch's header for changes in v2.

Dexuan Cui (2):
  vsock: remove the unused 'wait' in vsock_connectible_recvmsg()
  vsock: fix possible infinite sleep in vsock_connectible_wait_data()

[...]

Here is the summary with links:
  - [v2,1/2] vsock: remove the unused 'wait' in vsock_connectible_recvmsg()
    https://git.kernel.org/netdev/net/c/cf6ff0df0fd1
  - [v2,2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()
    https://git.kernel.org/netdev/net/c/466a85336fee

You are awesome, thank you!
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