From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 975C91DF73C; Tue, 30 Sep 2025 15:28:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759246092; cv=none; b=usimr4xcMj/U60Lc/ozKzWeczGkya9bx31gUVDMohaszRP40Zfky+3HbqKgTXBQBTRW80RE2MNKitCbl1oNf5P7tB1I05YSagPC65q0nNEYugwX+aDpilojgPKNkHwgz9rGNF7mjX/vCtIiigFDzPAzBFubHzNuiAsdIimcWX4w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759246092; c=relaxed/simple; bh=GttBQgNC03/EbcldbYrLlhtzc6DITGI/VcH1Wqx7tP0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W3j/Rv3MkGh3/O3wy+6BpamekWKVf3ORg32e7ATQcaOrjvxbBYUzJl9rLw+au0hAMj7DR2Dm6jeV/dHxbTVVil6lU40haHCFbSqdyMEThS6KwXqs7bSL2SqhBy4pGh31rzM4PZQr/r9HTnNBnytcuAkdncK18WkLZ/8ZjTGU2rw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Bh8K7jwQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Bh8K7jwQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04190C4CEF0; Tue, 30 Sep 2025 15:28:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759246092; bh=GttBQgNC03/EbcldbYrLlhtzc6DITGI/VcH1Wqx7tP0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Bh8K7jwQJrSI49xTURCAxLGzro/poRlYnAIEDy3sgyGhHg473GDvekBSiugDjQaPV llqHT5cEoR8XyTI+Hp31dasALOYfOAhM+cbD9QlTum/a/I//ueqWWkWQfGKJFvLqx/ OPhosUBQGD2X1I0tA3pl/DPPhW8Qbr1ZFBQxr+CA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sean Christopherson , Sebastian Andrzej Siewior , "Michael S. Tsirkin" , Sasha Levin Subject: [PATCH 6.12 50/89] vhost: Take a reference on the task in struct vhost_task. Date: Tue, 30 Sep 2025 16:48:04 +0200 Message-ID: <20250930143823.990693316@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143821.852512002@linuxfoundation.org> References: <20250930143821.852512002@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior [ Upstream commit afe16653e05db07d658b55245c7a2e0603f136c0 ] 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 Closes: https://lore.kernel.org/all/aKkLEtoDXKxAAWju@google.com/ Signed-off-by: Sebastian Andrzej Siewior Message-Id: <20250918181144.Ygo8BZ-R@linutronix.de> Signed-off-by: Michael S. Tsirkin Tested-by: Sean Christopherson Signed-off-by: Sasha Levin --- kernel/vhost_task.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c index 2f844c279a3e0..7f24ccc896c64 100644 --- a/kernel/vhost_task.c +++ b/kernel/vhost_task.c @@ -100,6 +100,7 @@ void vhost_task_stop(struct vhost_task *vtsk) * freeing it below. */ wait_for_completion(&vtsk->exited); + put_task_struct(vtsk->task); kfree(vtsk); } EXPORT_SYMBOL_GPL(vhost_task_stop); @@ -148,7 +149,7 @@ struct vhost_task *vhost_task_create(bool (*fn)(void *), return ERR_PTR(PTR_ERR(tsk)); } - vtsk->task = tsk; + vtsk->task = get_task_struct(tsk); return vtsk; } EXPORT_SYMBOL_GPL(vhost_task_create); -- 2.51.0