From patchwork Thu May 25 09:31:52 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Ogness X-Patchwork-Id: 686352 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 D8627C7EE2F for ; Thu, 25 May 2023 09:35:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240602AbjEYJen (ORCPT ); Thu, 25 May 2023 05:34:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240503AbjEYJek (ORCPT ); Thu, 25 May 2023 05:34:40 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF70919C; Thu, 25 May 2023 02:34:30 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1685007268; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4NGWDH2m9xz3zGie63zl1kcLGjTJ0fX1VflVrGzz2ZQ=; b=Kja8EByGHMg80rkSKT9+A6oAP7Ytw5mSKQu0+uGfVfwe5tVdGCEi5josuEM1SwN606+mom tJOhrFWIt2zJG+DlK5DjPmWfVz6loRqSChpbkp8HXvZab2zEzJXhmgL0k+AWUZunXGh4bK ZB+SftTZW59pKhVFlzUNZNYOpZMdX8zxvpepVbJv55/P+jYmWnd8ln/AejbG3dDoZJevAa J7Qto8rkUPaEA13Qh78iauHtxD9/MNjhQsamwocWO64h7fGgSzp5rGrAHv5Xn4mRXNmpig fi0pD7NC4PYFiEdTiZBJclw3eqzxfLzFQqzujGa99ba9O296DwZrG+8YpmfJ+w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1685007268; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4NGWDH2m9xz3zGie63zl1kcLGjTJ0fX1VflVrGzz2ZQ=; b=mmiTP6jCW1+KvC8QM+LWeB5WcVHbyStKgJqzDNEQsZrG0o3PYsrEqd/a7KE5S+4YPNPZjx 20P+WWxS57IdbmBQ== To: Greg Kroah-Hartman Cc: Petr Mladek , Thomas Gleixner , linux-kernel@vger.kernel.org, Al Cooper , Broadcom internal kernel review list , Jiri Slaby , =?utf-8?q?Ilpo_J=C3=A4rvinen?= , Lino Sanfilippo , Matthew Howell , Tony Lindgren , Lukas Wunner , Matthias Schiffer , Andy Shevchenko , =?utf-8?q?Uwe_Kleine-K?= =?utf-8?q?=C3=B6nig?= , linux-serial@vger.kernel.org Subject: [PATCH tty v1 1/8] serial: 8250: lock port in startup() callbacks Date: Thu, 25 May 2023 11:37:52 +0206 Message-Id: <20230525093159.223817-2-john.ogness@linutronix.de> In-Reply-To: <20230525093159.223817-1-john.ogness@linutronix.de> References: <20230525093159.223817-1-john.ogness@linutronix.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org uart_ops startup() callback is called without interrupts disabled and without port->lock locked, relatively late during the boot process (from the call path of console_on_rootfs()). If the device is a console, it was already previously registered and could be actively printing messages. The console printing function serial8250_console_write() modifies the interrupt register (UART_IER) under the port->lock with the pattern: read, clear, restore. Since some startup() callbacks are modifying UART_IER without the port->lock locked, it is possible that the value intended to be written by the startup() callback will get overwritten and be lost. CPU0 CPU1 serial8250_console_write omap_8250_startup -------------------------- ----------------- spin_lock(port->lock) oldval = read(UART_IER) uart_console_write() write(newval, UART_IER) write(oldval, UART_IER) spin_unlock(port->lock) Add port->lock synchronization to the 8250 startup() callbacks where they need to access UART_IER. This avoids racing with serial8250_console_write(). Signed-off-by: John Ogness --- drivers/tty/serial/8250/8250_bcm7271.c | 4 ++++ drivers/tty/serial/8250/8250_exar.c | 4 ++++ drivers/tty/serial/8250/8250_omap.c | 3 +++ drivers/tty/serial/8250/8250_port.c | 18 ++++++++++++++++-- 4 files changed, 27 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c index f801b1f5b46c..2b38bcc5112e 100644 --- a/drivers/tty/serial/8250/8250_bcm7271.c +++ b/drivers/tty/serial/8250/8250_bcm7271.c @@ -605,9 +605,13 @@ static int brcmuart_startup(struct uart_port *port) /* * Disable the Receive Data Interrupt because the DMA engine * will handle this. + * + * Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); up->ier &= ~UART_IER_RDI; serial_port_out(port, UART_IER, up->ier); + spin_unlock_irq(&port->lock); priv->tx_running = false; priv->dma.rx_dma = NULL; diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c index 64770c62bbec..ae66ef9d863c 100644 --- a/drivers/tty/serial/8250/8250_exar.c +++ b/drivers/tty/serial/8250/8250_exar.c @@ -194,8 +194,12 @@ static int xr17v35x_startup(struct uart_port *port) /* * Make sure all interrups are masked until initialization is * complete and the FIFOs are cleared + * + * Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); serial_port_out(port, UART_IER, 0); + spin_unlock_irq(&port->lock); return serial8250_do_startup(port); } diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 5c093dfcee1d..fbca0692aa51 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -710,8 +710,11 @@ static int omap_8250_startup(struct uart_port *port) up->dma = NULL; } + /* Synchronize UART_IER access against the console. */ + spin_lock_irq(&port->lock); up->ier = UART_IER_RLSI | UART_IER_RDI; serial_out(up, UART_IER, up->ier); + spin_unlock_irq(&port->lock); #ifdef CONFIG_PM up->capabilities |= UART_CAP_RPM; diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 0cef9bfd0471..b3971302d8e5 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2149,7 +2149,12 @@ int serial8250_do_startup(struct uart_port *port) serial8250_rpm_get(up); if (port->type == PORT_16C950) { - /* Wake up and initialize UART */ + /* + * Wake up and initialize UART + * + * Synchronize UART_IER access against the console. + */ + spin_lock_irqsave(&port->lock, flags); up->acr = 0; serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B); serial_port_out(port, UART_EFR, UART_EFR_ECB); @@ -2159,12 +2164,19 @@ int serial8250_do_startup(struct uart_port *port) serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B); serial_port_out(port, UART_EFR, UART_EFR_ECB); serial_port_out(port, UART_LCR, 0); + spin_unlock_irqrestore(&port->lock, flags); } if (port->type == PORT_DA830) { - /* Reset the port */ + /* + * Reset the port + * + * Synchronize UART_IER access against the console. + */ + spin_lock_irqsave(&port->lock, flags); serial_port_out(port, UART_IER, 0); serial_port_out(port, UART_DA830_PWREMU_MGMT, 0); + spin_unlock_irqrestore(&port->lock, flags); mdelay(10); /* Enable Tx, Rx and free run mode */ @@ -2275,6 +2287,8 @@ int serial8250_do_startup(struct uart_port *port) * this interrupt whenever the transmitter is idle and * the interrupt is enabled. Delays are necessary to * allow register changes to become visible. + * + * Synchronize UART_IER access against the console. */ spin_lock_irqsave(&port->lock, flags);