From: Sean Christopherson <seanjc@google.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jason Wang <jasowang@redhat.com>,
kvm@vger.kernel.org, virtualization@lists.linux.dev,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] vhost: Take a reference on the task that is reference in struct vhost_task.
Date: Fri, 19 Sep 2025 14:15:45 -0700 [thread overview]
Message-ID: <aM3IAaCVx-PDeDsi@google.com> (raw)
In-Reply-To: <20250918181144.Ygo8BZ-R@linutronix.de>
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@google.com>
> Closes: https://lore.kernel.org/all/aKkLEtoDXKxAAWju@google.com/
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
Tested-by: Sean Christopherson <seanjc@google.com>
next prev parent reply other threads:[~2025-09-19 21:15 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-27 19:41 [PATCH v2 0/3] vhost_task: Fix a bug where KVM wakes an exited task Sean Christopherson
2025-08-27 19:41 ` [PATCH v2 1/3] vhost_task: Don't wake KVM x86's recovery thread if vhost task was killed Sean Christopherson
2025-08-27 19:41 ` [PATCH v2 2/3] vhost_task: Allow caller to omit handle_sigkill() callback Sean Christopherson
2025-08-27 19:41 ` [PATCH v2 3/3] KVM: x86/mmu: Don't register a sigkill callback for NX hugepage recovery tasks Sean Christopherson
2025-08-27 20:10 ` [PATCH v2 0/3] vhost_task: Fix a bug where KVM wakes an exited task Sebastian Andrzej Siewior
2025-08-28 0:16 ` Sean Christopherson
2025-08-28 6:48 ` Sebastian Andrzej Siewior
2025-09-15 22:23 ` Michael S. Tsirkin
2025-08-28 2:42 ` Lei Yang
2025-09-18 15:09 ` Michael S. Tsirkin
2025-09-18 15:48 ` Sebastian Andrzej Siewior
2025-09-18 16:04 ` Sean Christopherson
2025-09-18 16:08 ` Michael S. Tsirkin
2025-09-18 16:52 ` Sean Christopherson
2025-09-18 17:40 ` Michael S. Tsirkin
2025-09-18 17:58 ` Sean Christopherson
2025-09-18 16:06 ` Michael S. Tsirkin
2025-09-18 18:11 ` [PATCH] vhost: Take a reference on the task that is reference in struct vhost_task Sebastian Andrzej Siewior
2025-09-19 21:15 ` Sean Christopherson [this message]
2025-09-21 20:56 ` Michael S. Tsirkin
2025-09-21 21:40 ` Michael S. Tsirkin
2025-09-15 21:03 ` [PATCH v2 0/3] vhost_task: Fix a bug where KVM wakes an exited task Sean Christopherson
2025-09-15 22:20 ` Michael S. Tsirkin
2025-09-15 22:22 ` Sean Christopherson
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