linux-kernel - Re: [PATCH] serial: sh-sci: disable DMA for uart

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20190513154306.GA6060@mam-gdavis-lt>
Date:   Mon, 13 May 2019 11:43:06 -0400
From:   "George G. Davis" <george_davis@...tor.com>
To:     Wolfram Sang <wsa@...-dreams.de>
CC:     "George G. Davis" <ggdavisiv@...il.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Simon Horman <horms+renesas@...ge.net.au>,
        Chris Brandt <chris.brandt@...esas.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Ulrich Hecht <ulrich.hecht+renesas@...il.com>,
        Andy Lowe <andy_lowe@...tor.com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS 
        <devicetree@...r.kernel.org>, Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] serial: sh-sci: disable DMA for uart_console

Hello Wolfram,

On Mon, May 13, 2019 at 03:51:14PM +0200, Wolfram Sang wrote:
> On Thu, May 09, 2019 at 10:43:30AM -0400, George G. Davis wrote:
> > As noted in commit 84b40e3b57ee ("serial: 8250: omap: Disable DMA for
> > console UART"), UART console lines use low-level PIO only access functions
> > which will conflict with use of the line when DMA is enabled, e.g. when
> > the console line is also used for systemd messages. So disable DMA
> > support for UART console lines.
> > 
> > Fixes: https://patchwork.kernel.org/patch/10929511/
> > Reported-by: Michael Rodin <mrodin@...adit-jv.com>
> > Cc: Eugeniu Rosca <erosca@...adit-jv.com>
> > Signed-off-by: George G. Davis <george_davis@...tor.com>
> > ---
> >  drivers/tty/serial/sh-sci.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> > index 3cd139752d3f..885b56b1d4e4 100644
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -1557,6 +1557,9 @@ static void sci_request_dma(struct uart_port *port)
> >  
> >  	dev_dbg(port->dev, "%s: port %d\n", __func__, port->line);
> >  
> > +	if (uart_console(port))
> > +		return; /* Cannot use DMA on console */
> 
> Minor nit: maybe the comment can be made more specific?
> 
> /*
>  * DMA on console may interfere with Kernel log messages which use
>  * plain putchar(). So, simply don't use it with a console.
>  */

I'll submit v2 with the above recommended change.

Thanks!

> Other than that:
> 
> Reviewed-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> 
> Much better than dropping the properties, as Geert noted.

-- 
Regards,
George