linux-kernel - Re: [PATCH] arm64: CONFIG_DEVPORT should not be used when PCI is being used

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Message-ID: <20160407001819.GB9228@kroah.com>
Date:	Wed, 6 Apr 2016 17:18:19 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Al Stone <ahs3@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] arm64: CONFIG_DEVPORT should not be used when PCI is
 being used

On Wed, Apr 06, 2016 at 03:27:20PM -0600, Al Stone wrote:
> On arm64 systems, using /dev/port does not really make sense; this is
> historically used for other architectures to access ISA IO ports, which
> with any luck do not exist on arm64 platforms.  With the following snippet
> of perl code (from Jeff Bastian <jbastian@...hat.com>), we can reliably
> panic an arm64 system with PCI enabled:
> 
> 	#!/usr/bin/perl -w
> 	# extracted from sensors-detect from lm_sensors
> 	# to reproduce kernel crash when probing the
> 	# Super-I/O ports
> 	use Fcntl qw(:DEFAULT :seek);
> 	sysopen(IOPORTS, "/dev/port", O_RDWR);
> 	binmode(IOPORTS);
> 	sysseek(IOPORTS, 0x2e, 0);
> 	syswrite(IOPORTS, pack("C", 0x0d), 1);
> 
> So, make sure CONFIG_DEVPORT cannot be set on arm64; it cannot really be
> used and it allows us to crash a kernel from user space.
> 
> Signed-off-by: Al Stone <ahs3@...hat.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  drivers/char/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
> index b272397..c532f62 100644
> --- a/drivers/char/Kconfig
> +++ b/drivers/char/Kconfig
> @@ -587,7 +587,7 @@ config TELCLOCK
>  
>  config DEVPORT
>  	bool
> -	depends on !M68K
> +	depends on !M68K && !ARM64

Why not fix the real bug here, it's odd that only these two arches need
this disabled, don't you agree?

thanks,

greg k-h