netdev - Re: [PATCH] vhost: Take a reference on the task that is reference in struct vhost

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Message-ID: <aM3IAaCVx-PDeDsi@google.com>
Date: Fri, 19 Sep 2025 14:15:45 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Jason Wang <jasowang@...hat.com>, kvm@...r.kernel.org, virtualization@...ts.linux.dev, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vhost: Take a reference on the task that is reference in
 struct vhost_task.

On Thu, Sep 18, 2025, Sebastian Andrzej Siewior wrote:
> vhost_task_create() creates a task and keeps a reference to its
> task_struct. That task may exit early via a signal and its task_struct
> will be released.
> A pending vhost_task_wake() will then attempt to wake the task and
> access a task_struct which is no longer there.
> 
> Acquire a reference on the task_struct while creating the thread and
> release the reference while the struct vhost_task itself is removed.
> If the task exits early due to a signal, then the vhost_task_wake() will
> still access a valid task_struct. The wake is safe and will be skipped
> in this case.
> 
> Fixes: f9010dbdce911 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression")
> Reported-by: Sean Christopherson <seanjc@...gle.com>
> Closes: https://lore.kernel.org/all/aKkLEtoDXKxAAWju@google.com/
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---

Tested-by: Sean Christopherson <seanjc@...gle.com>