linux-kernel - Re: [PATCH v4 5/5] serial/8250: Only use fifo after the port is initialized in console

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

Message-ID: <4914513f-cdb8-7698-be7f-968d343c5693@kernel.org>
Date:   Thu, 17 Mar 2022 08:06:39 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Wander Lairson Costa <wander@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        Serge Semin <fancer.lancer@...il.com>,
        Lukas Wunner <lukas@...ner.de>,
        Pali Rohár <pali@...nel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Cc:     rostedt@...dmis.org, senozhatsky@...omium.org,
        andre.goddard@...il.com, sudipm.mukherjee@...il.com,
        andy.shevchenko@...il.com, David.Laight@...lab.com,
        jonathanh@...dia.com, phil@...pberrypi.com
Subject: Re: [PATCH v4 5/5] serial/8250: Only use fifo after the port is
 initialized in console_write

On 16. 03. 22, 15:36, Wander Lairson Costa wrote:
> The serial driver set the value of uart_8250_port.fcr in the function
> serial8250_config_port, but only writes the value to the controller
> register later in the initalization code.
> 
> That opens a small window in which is not safe to use the fifo for
> console write.
> 
> Make sure the port is initialized correctly before reading the FCR
> cached value.
> 
> Unfortunately, I lost track of who originally reported the issue. If
> s/he is reading this, please speak up so I can give you the due credit.
> 
> Signed-off-by: Wander Lairson Costa <wander@...hat.com>
> ---
>   drivers/tty/serial/8250/8250_port.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 4acf620be241..7e2227161555 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -3416,6 +3416,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
>   		!(up->capabilities & UART_CAP_MINI) &&
>   		up->tx_loadsz > 1 &&
>   		(up->fcr & UART_FCR_ENABLE_FIFO) &&
> +		test_bit(TTY_PORT_INITIALIZED, &port->state->port.iflags) &&

Cannot be port->state be NULL sometimes here?

>   		/*
>   		 * After we put a data in the fifo, the controller will send
>   		 * it regardless of the CTS state. Therefore, only use fifo


-- 
js
suse labs