Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DBC5C6FD19 for ; Mon, 6 Mar 2023 09:00:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229696AbjCFJAW (ORCPT ); Mon, 6 Mar 2023 04:00:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35844 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229557AbjCFJAT (ORCPT ); Mon, 6 Mar 2023 04:00:19 -0500 Received: from mta-64-228.siemens.flowmailer.net (mta-64-228.siemens.flowmailer.net [185.136.64.228]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2FBBD3C14 for ; Mon, 6 Mar 2023 01:00:17 -0800 (PST) Received: by mta-64-228.siemens.flowmailer.net with ESMTPSA id 202303060900142a43b2a92db8f82103 for ; Mon, 06 Mar 2023 10:00:14 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=fm1; d=siemens.com; i=alexander.sverdlin@siemens.com; h=Date:From:Subject:To:Message-ID:MIME-Version:Content-Type:Content-Transfer-Encoding:Cc; bh=pIZj8+zdp8ZkWBypoawgPOIV+bNHdnfVxMzVLAvkRvo=; b=QHcpR46b0lgdpqR4RkuOwCPQFLP2NDPEfi9rXnCyFKcI4WkkLWSNIEXuOfnjgwMAv0gZFo kYEj8z0wAhiZrWzZ5ID38i1YTGC56mZZo5CXAU4GfJII9EwebnaRJGqz6NBmsZ7LQRFC+xwd U4795NN0Y3oXLasr8qEQM11ApcotY=; From: "A. Sverdlin" To: linux-serial@vger.kernel.org Cc: Alexander Sverdlin , Greg Kroah-Hartman , Jiri Slaby , linux-kernel@vger.kernel.org Subject: [PATCH] tty: serial: fsl_lpuart: fix race on RX DMA shutdown Date: Mon, 6 Mar 2023 10:00:11 +0100 Message-Id: <20230306090011.80725-1-alexander.sverdlin@siemens.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Flowmailer-Platform: Siemens Feedback-ID: 519:519-456497:519-21489:flowmailer Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexander Sverdlin From time to time DMA completion can come in the middle of DMA shutdown: : : lpuart32_shutdown() lpuart_dma_shutdown() del_timer_sync() lpuart_dma_rx_complete() lpuart_copy_rx_to_tty() mod_timer() lpuart_dma_rx_free() When the timer fires a bit later, sport->dma_rx_desc is NULL: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004 pc : lpuart_copy_rx_to_tty+0xcc/0x5bc lr : lpuart_timer_func+0x1c/0x2c Call trace: lpuart_copy_rx_to_tty lpuart_timer_func call_timer_fn __run_timers.part.0 run_timer_softirq __do_softirq __irq_exit_rcu irq_exit handle_domain_irq gic_handle_irq call_on_irq_stack do_interrupt_handler ... To fix this fold del_timer_sync() into lpuart_dma_rx_free() after dmaengine_terminate_sync() to make sure timer will not be re-started in lpuart_copy_rx_to_tty() <= lpuart_dma_rx_complete(). Signed-off-by: Alexander Sverdlin --- drivers/tty/serial/fsl_lpuart.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index e945f41b93d43..47c267ee22e04 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1354,6 +1354,7 @@ static void lpuart_dma_rx_free(struct uart_port *port) struct dma_chan *chan = sport->dma_rx_chan; dmaengine_terminate_sync(chan); + del_timer_sync(&sport->lpuart_timer); dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE); kfree(sport->rx_ring.buf); sport->rx_ring.tail = 0; @@ -1813,7 +1814,6 @@ static int lpuart32_startup(struct uart_port *port) static void lpuart_dma_shutdown(struct lpuart_port *sport) { if (sport->lpuart_dma_rx_use) { - del_timer_sync(&sport->lpuart_timer); lpuart_dma_rx_free(&sport->port); sport->lpuart_dma_rx_use = false; } @@ -1973,10 +1973,8 @@ lpuart_set_termios(struct uart_port *port, struct ktermios *termios, * Since timer function acqures sport->port.lock, need to stop before * acquring same lock because otherwise del_timer_sync() can deadlock. */ - if (old && sport->lpuart_dma_rx_use) { - del_timer_sync(&sport->lpuart_timer); + if (old && sport->lpuart_dma_rx_use) lpuart_dma_rx_free(&sport->port); - } spin_lock_irqsave(&sport->port.lock, flags); @@ -2210,10 +2208,8 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, * Since timer function acqures sport->port.lock, need to stop before * acquring same lock because otherwise del_timer_sync() can deadlock. */ - if (old && sport->lpuart_dma_rx_use) { - del_timer_sync(&sport->lpuart_timer); + if (old && sport->lpuart_dma_rx_use) lpuart_dma_rx_free(&sport->port); - } spin_lock_irqsave(&sport->port.lock, flags); @@ -3014,7 +3010,6 @@ static int lpuart_suspend(struct device *dev) * cannot resume as expected, hence gracefully release the * Rx DMA path before suspend and start Rx DMA path on resume. */ - del_timer_sync(&sport->lpuart_timer); lpuart_dma_rx_free(&sport->port); /* Disable Rx DMA to use UART port as wakeup source */ -- 2.34.1