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 33AC11EE02F; Tue, 30 Sep 2025 15:04:03 +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=1759244643; cv=none; b=nelrgkRfV2oe+Nadphd8UKwpm5ra/vaTjXZMXKyJERjq3uca/Wqzb3boa1mWiFsmQ/Onk/vDbvcaJ2FnKBediRdtX6ezZXCwDct+YcCuK5kagTTzb7N8Vb3bmzd2swiMju3Y7/NLn9iCBuU45Kzukdw3JltFfemDUnyVC8sb4Vo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244643; c=relaxed/simple; bh=6C0m5btIEBUMFUj1myMdF9sJ90aF6ztZ0sO/sJ95hHU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=V8O0gWrs0yK3E6uYx1sfxy4wJULy70cj+UHtyEMp7uMZPf8Ibxtmf7SO9k4W8hQ1uAagTwH6cqqXhUNJv3xn9WulevR6AyZ4QmUtje6LMVzbca7N2U3tg7EkwAKUVckQGTGymGD5CEgBwSKBT3Ff3sOfyb4N040o+Xd/A1ueicE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cJkUa/hj; 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="cJkUa/hj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9962C4CEF0; Tue, 30 Sep 2025 15:04:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759244643; bh=6C0m5btIEBUMFUj1myMdF9sJ90aF6ztZ0sO/sJ95hHU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cJkUa/hjQaQ0kjo0I7EslTVea8Y33Z9gvXb8udM41ImE2ge/n9/mECl2NfszzMTxR z41Jt6Wa9tY5/QuC350kgxtbJj54uPTyJakai+AkbBOqgzBxavjcsXyfyoDjep/rei TiL+n3Z3npjKmRIVkbK1Hq/2V70KmjfevrxwEtOo= 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 6.16 071/143] vhost: Take a reference on the task in struct vhost_task. Date: Tue, 30 Sep 2025 16:46:35 +0200 Message-ID: <20250930143834.068575454@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143831.236060637@linuxfoundation.org> References: <20250930143831.236060637@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 6.16-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