[v2] vsock: remove an unused variable and fix infinite sleep

[PATCH v2 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()

Posted by Dexuan Cui 3 years, 5 months ago

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

Re: [PATCH v2 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()

Posted by Stefano Garzarella 3 years, 5 months ago

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>

>
> 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
>

Re: [PATCH v2 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()

Posted by Stefano Garzarella 3 years, 5 months ago

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:
>>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 <frederic.dalleau@docker.com>

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

Re: [PATCH v2 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()

Posted by Frederic Dalleau 3 years, 5 months ago

Hi Dexuan, Stefano,

Tested-by: Frédéric Dalleau <frederic.dalleau@docker.com>

Regards,
Frédéric


On Wed, Nov 2, 2022 at 10:42 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> 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:
> >>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 <frederic.dalleau@docker.com>
>
> 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
>

RE: [PATCH v2 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()

Posted by Dexuan Cui 3 years, 5 months ago

> From: Frederic Dalleau <frederic.dalleau@docker.com>
> Sent: Wednesday, November 2, 2022 6:31 AM
> To: Stefano Garzarella <sgarzare@redhat.com>
> ...
> Hi Dexuan, Stefano,
> 
> Tested-by: Frédéric Dalleau <frederic.dalleau@docker.com>
> 
> Regards,
> Frédéric

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

Thanks Stefano for reviewing!

Thanks,
-- Dexuan