From mboxrd@z Thu Jan 1 00:00:00 1970 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46FC4C433EF for ; Mon, 8 Nov 2021 09:18:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 270D5611C0 for ; Mon, 8 Nov 2021 09:18:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238326AbhKHJUp (ORCPT ); Mon, 8 Nov 2021 04:20:45 -0500 Received: from guitar.tcltek.co.il ([192.115.133.116]:50482 "EHLO mx.tkos.co.il" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238319AbhKHJUh (ORCPT ); Mon, 8 Nov 2021 04:20:37 -0500 Received: from tarshish (unknown [10.0.8.3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx.tkos.co.il (Postfix) with ESMTPS id 3B9E6440F4F; Mon, 8 Nov 2021 11:17:35 +0200 (IST) Authentication-Results: mx.tkos.co.il; dmarc=fail header.from=tkos.co.il DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=tkos.co.il; s=default; t=1636363055; bh=EdySZS6fF+LC1Glq5J2sGIomHJdBAbbglhDfcVAI94Y=; h=References:From:To:Cc:Subject:Date:In-reply-to:From; b=KkyeSOVi0f2AoKNA6IKQOibNDlJtKmiy8EzpNL/w+6pOpz0AFm4rTqi/JEHmLPs7j JnOAPMXIOmf6zuIK8vSl3dAT5m9i9Wk028IKJdhnUHJQ8cbQLWTNhtIPbpCR3W9VmS i/A5yPnWJ57xWK9wSAh70in3prh6OOxcJ1zWDl7fO+CvL2wTdu9xBET7VSbM2cqJyf R2+sAICbyXNm46dxpkQ0BPS8dHSH067g1I8jLksXwSLUSvj/iH1HhVyhghpeXUjfhm CEkFPd80h80p2f4ckXycCrhYQJZ//1UIcnDr+x0u1rrpgaceIURROOLdVrkskvQO9J ZYF/HI+6TWeDg== References: <20211108085431.12637-1-johan@kernel.org> User-agent: mu4e 1.6.9; emacs 27.1 From: Baruch Siach To: Johan Hovold Cc: Greg Kroah-Hartman , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Rob Herring Subject: Re: [PATCH] serial: core: fix transmit-buffer reset and memleak Date: Mon, 08 Nov 2021 11:15:56 +0200 In-reply-to: <20211108085431.12637-1-johan@kernel.org> Message-ID: <87mtmfuhtx.fsf@tarshish> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Johan, On Mon, Nov 08 2021, Johan Hovold wrote: > Commit 761ed4a94582 ("tty: serial_core: convert uart_close to use > tty_port_close") converted serial core to use tty_port_close() but > failed to notice that the transmit buffer still needs to be freed on > final close. > > Not freeing the transmit buffer means that the buffer is no longer > cleared on next open so that any ioctl() waiting for the buffer to drain > might wait indefinitely (e.g. on termios changes) or that stale data can > end up being transmitted in case tx is restarted. > > Furthermore, the buffer of any port that has been opened would leak on > driver unbind. > > Note that the port lock is held when clearing the buffer pointer due to > the ldisc race worked around by commit a5ba1d95e46e ("uart: fix race > between uart_put_char() and uart_shutdown()"). > > Also note that the tty-port shutdown() callback is not called for > console ports so it is not strictly necessary to free the buffer page > after releasing the lock (cf. d72402145ace ("tty/serial: do not free > trasnmit buffer page under port lock")). > > Reported-by: Baruch Siach > Link: https://lore.kernel.org/r/319321886d97c456203d5c6a576a5480d07c3478.1635781688.git.baruch@tkos.co.il > Fixes: 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close") > Cc: stable@vger.kernel.org # 4.9 > Cc: Rob Herring > Signed-off-by: Johan Hovold Thanks for the analysis and root cause fix. This patch also fixes the issue for me. Tested-by: Baruch Siach baruch > --- > drivers/tty/serial/serial_core.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > index 0e2e35ab64c7..58834698739c 100644 > --- a/drivers/tty/serial/serial_core.c > +++ b/drivers/tty/serial/serial_core.c > @@ -1542,6 +1542,7 @@ static void uart_tty_port_shutdown(struct tty_port *port) > { > struct uart_state *state = container_of(port, struct uart_state, port); > struct uart_port *uport = uart_port_check(state); > + char *buf; > > /* > * At this point, we stop accepting input. To do this, we > @@ -1563,8 +1564,18 @@ static void uart_tty_port_shutdown(struct tty_port *port) > */ > tty_port_set_suspended(port, 0); > > - uart_change_pm(state, UART_PM_STATE_OFF); > + /* > + * Free the transmit buffer. > + */ > + spin_lock_irq(&uport->lock); > + buf = state->xmit.buf; > + state->xmit.buf = NULL; > + spin_unlock_irq(&uport->lock); > > + if (buf) > + free_page((unsigned long)buf); > + > + uart_change_pm(state, UART_PM_STATE_OFF); > } > > static void uart_wait_until_sent(struct tty_struct *tty, int timeout) -- ~. .~ Tk Open Systems =}------------------------------------------------ooO--U--Ooo------------{= - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -