Re: [PATCH 09/39] Annotate hardware config module parameters in drivers/i2c/

[Jean Delvare]

Hi David,

On jeu., 2016-12-01 at 12:30 +0000, David Howells wrote:
> When the kernel is running in secure boot mode, we lock down the kernel to
> prevent userspace from modifying the running kernel image.  Whilst this
> includes prohibiting access to things like /dev/mem, it must also prevent
> access by means of configuring driver modules in such a way as to cause a
> device to access or modify the kernel image.
> 
> To this end, annotate module_param* statements that refer to hardware
> configuration and indicate for future reference what type of parameter they
> specify.  The parameter parser in the core sees this information and can
> skip such parameters with an error message if the kernel is locked down.
> The module initialisation then runs as normal, but just sees whatever the
> default values for those parameters is.
> 
> Note that we do still need to do the module initialisation because some
> drivers have viable defaults set in case parameters aren't specified and
> some drivers support automatic configuration (e.g. PNP or PCI) in addition
> to manually coded parameters.

Initializing the driver when you are not able to honor the user request
looks wrong to me. I don't see how some drivers having sane defaults
justifies that. Using the defaults when no parameters are passed is one
thing (good), still using the defaults when parameters are passed is
another (bad), and you should be able to differentiate between these two
cases.

> This patch annotates drivers in drivers/i2c/.
> 
> Suggested-by: One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx>

I know this is only a Suggested-by and not a Signed-off-by, but still I
believe the Developer's Certificate of Origin applies, and it says:
"using your real name (sorry, no pseudonyms or anonymous
contributions.)"

> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> cc: Jean Delvare <jdelvare@xxxxxxxx>
> cc: linux-i2c@xxxxxxxxxxxxxxx
> ---
> 
>  drivers/i2c/busses/i2c-elektor.c       |    6 +++---
>  drivers/i2c/busses/i2c-parport-light.c |    4 ++--
>  drivers/i2c/busses/i2c-pca-isa.c       |    4 ++--
>  drivers/i2c/busses/scx200_acb.c        |    2 +-
>  4 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-elektor.c b/drivers/i2c/busses/i2c-elektor.c
> index 8af62fb3fe41..5416003e0605 100644
> --- a/drivers/i2c/busses/i2c-elektor.c
> +++ b/drivers/i2c/busses/i2c-elektor.c
> @@ -323,9 +323,9 @@ MODULE_AUTHOR("Hans Berglund <hb@xxxxxxxxxxx>");
>  MODULE_DESCRIPTION("I2C-Bus adapter routines for PCF8584 ISA bus adapter");
>  MODULE_LICENSE("GPL");
>  
> -module_param(base, int, 0);
> -module_param(irq, int, 0);
> +module_param_hw(base, int, ioport_or_iomem, 0);
> +module_param_hw(irq, int, irq, 0);
>  module_param(clock, int, 0);
>  module_param(own, int, 0);
> -module_param(mmapped, int, 0);
> +module_param_hw(mmapped, int, other, 0);
>  module_isa_driver(i2c_elektor_driver, 1);
> diff --git a/drivers/i2c/busses/i2c-parport-light.c b/drivers/i2c/busses/i2c-parport-light.c
> index 1bcdd10b68b9..faa8fb8f2b8f 100644
> --- a/drivers/i2c/busses/i2c-parport-light.c
> +++ b/drivers/i2c/busses/i2c-parport-light.c
> @@ -38,11 +38,11 @@
>  static struct platform_device *pdev;
>  
>  static u16 base;
> -module_param(base, ushort, 0);
> +module_param_hw(base, ushort, ioport, 0);
>  MODULE_PARM_DESC(base, "Base I/O address");
>  
>  static int irq;
> -module_param(irq, int, 0);
> +module_param_hw(irq, int, irq, 0);
>  MODULE_PARM_DESC(irq, "IRQ (optional)");
>  
>  /* ----- Low-level parallel port access ----------------------------------- */
> diff --git a/drivers/i2c/busses/i2c-pca-isa.c b/drivers/i2c/busses/i2c-pca-isa.c
> index ba88f17f636c..946ac646de2a 100644
> --- a/drivers/i2c/busses/i2c-pca-isa.c
> +++ b/drivers/i2c/busses/i2c-pca-isa.c
> @@ -197,9 +197,9 @@ MODULE_AUTHOR("Ian Campbell <icampbell@xxxxxxxxx>");
>  MODULE_DESCRIPTION("ISA base PCA9564/PCA9665 driver");
>  MODULE_LICENSE("GPL");
>  
> -module_param(base, ulong, 0);
> +module_param_hw(base, ulong, ioport, 0);
>  MODULE_PARM_DESC(base, "I/O base address");
> -module_param(irq, int, 0);
> +module_param_hw(irq, int, irq, 0);
>  MODULE_PARM_DESC(irq, "IRQ");
>  module_param(clock, int, 0);
>  MODULE_PARM_DESC(clock, "Clock rate in hertz.\n\t\t"
> diff --git a/drivers/i2c/busses/scx200_acb.c b/drivers/i2c/busses/scx200_acb.c
> index 0a7e410b6195..e0923bee8d1f 100644
> --- a/drivers/i2c/busses/scx200_acb.c
> +++ b/drivers/i2c/busses/scx200_acb.c
> @@ -42,7 +42,7 @@ MODULE_LICENSE("GPL");
>  
>  #define MAX_DEVICES 4
>  static int base[MAX_DEVICES] = { 0x820, 0x840 };
> -module_param_array(base, int, NULL, 0);
> +module_param_hw_array(base, int, ioport, NULL, 0);
>  MODULE_PARM_DESC(base, "Base addresses for the ACCESS.bus controllers");
>  
>  #define POLL_TIMEOUT	(HZ/5)
> 
> 

No objection from me, but I think you missed several i2c bus driver
parameters:

i2c-ali15x3.c:module_param(force_addr, ushort, 0);
i2c-piix4.c:module_param (force_addr, int, 0);
i2c-sis5595.c:module_param(force_addr, ushort, 0);
i2c-viapro.c:module_param(force_addr, ushort, 0);

And maybe the following ones, but I'm not sure if forcibly enabling a
device is part of what you need to prevent:

i2c-piix4.c:module_param (force, int, 0);
i2c-sis630.c:module_param(force, bool, 0);
i2c-viapro.c:module_param(force, bool, 0);


-- 
Jean Delvare
SUSE L3 Support