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 E03A7846F; Tue, 30 Sep 2025 15:22:46 +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=1759245767; cv=none; b=o0tM3u36Z3tFaKcbqHs0E4XjEDGQKfDAeD8vVqlZfi/+EmBd73X6WutFPvDWmr0NGJ2o7sozjYiN7SrItJIitjx7zeYVdicQvePU6TrjbWewRCAWvsHWOVMOXfyX5ANsvfePl75h+I8ALii/CFS7rBTg8kS0D0r/7vmLjKTPjmg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759245767; c=relaxed/simple; bh=hcMTHqJvgv54wFaBVKnGDm+i1DdExOIMLTO4V1Wd6uc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AwSUHJcTAnCNSPbBmp+zUVLKsFXZnr/HssJ2iRpXuu+yLHB/NBAEvkYR9mxxKr/jGxSNnUsKHXzCTbRYLfIlq6m4D+dONJgoBuVYjOOlAA7x9BBQ+9v0huvhQZ+p7kPuguT/yw3qbwDg0suou54UiD+Kb72ltA3hJrPA/IMf4ec= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Wn0uru/U; 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="Wn0uru/U" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C54DC4CEF0; Tue, 30 Sep 2025 15:22:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759245766; bh=hcMTHqJvgv54wFaBVKnGDm+i1DdExOIMLTO4V1Wd6uc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Wn0uru/UntfonZ+rUYNGvM4Ls7dT4+tfskbaDxjoQgoeJXiVW1wYFUJhrxI28mzn9 LN3KLcTPaaUKXFh0PC0p/5rg3QPDsMxZhMaQjjAmTOys+mmn1MTVBB+17OqKwk8FSe 7l0zsyxI/Y0WCUJYoL5RnNmhpbuGCQNUgcqhWgmQ= 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 6.6 43/91] vhost: Take a reference on the task in struct vhost_task. Date: Tue, 30 Sep 2025 16:47:42 +0200 Message-ID: <20250930143822.961025954@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143821.118938523@linuxfoundation.org> References: <20250930143821.118938523@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 6.6-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 8800f5acc0071..5a2116356428f 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 NULL; } - vtsk->task = tsk; + vtsk->task = get_task_struct(tsk); return vtsk; } EXPORT_SYMBOL_GPL(vhost_task_create); -- 2.51.0