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

Submitted by David Howells on Dec. 1, 2016, 12:30 p.m.

Details

Message ID 148059544784.31612.17605303556663485588.stgit@warthog.procyon.org.uk
State New
Headers show

Commit Message

David Howells Dec. 1, 2016, 12:30 p.m.
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.

This patch annotates drivers in drivers/i2c/.

Suggested-by: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Wolfram Sang <wsa@the-dreams.de>
cc: Jean Delvare <jdelvare@suse.com>
cc: linux-i2c@vger.kernel.org
---

 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(-)


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Comments

Jean Delvare Dec. 1, 2016, 1:47 p.m.
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@lxorguk.ukuu.org.uk>

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@redhat.com>
> cc: Wolfram Sang <wsa@the-dreams.de>
> cc: Jean Delvare <jdelvare@suse.com>
> cc: linux-i2c@vger.kernel.org
> ---
> 
>  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@spacetec.no>");
>  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@arcom.com>");
>  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);
David Howells Dec. 1, 2016, 2:12 p.m.
Jean Delvare <jdelvare@suse.de> wrote:

> > 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.

Corey Minyard argues the other way:

	This would prevent any IPMI interface from working if any address was
	given on the kernel command line. I'm not sure what the best policy
	is, but that sounds like a possible DOS to me.

Your preference allows someone to prevent a driver from initialising - which
could also be bad.  The problem is that I don't think there's any way to do
both.

Note that the policy isn't actually handled in any of these patches, but will
be handled in a later patchset that is on top of my EFI changes also.

> > Suggested-by: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
> 
> 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.)"

I asked him what he prefers - but no response.

> 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);

Okay, thanks.  They all seem to encode ioports.  All changed.

> 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);

I don't know either.  One could argue it *should* be locked down because its
need appears to reflect a BIOS bug.

David
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Jean Delvare Dec. 1, 2016, 4:06 p.m.
On jeu., 2016-12-01 at 14:12 +0000, David Howells wrote:
> Jean Delvare <jdelvare@suse.de> wrote:
> 
> > > 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.
> 
> Corey Minyard argues the other way:
> 
> 	This would prevent any IPMI interface from working if any address was
> 	given on the kernel command line. I'm not sure what the best policy
> 	is, but that sounds like a possible DOS to me.
> 
> Your preference allows someone to prevent a driver from initialising - which
> could also be bad.  The problem is that I don't think there's any way to do
> both.

I'm not sure what is your threat model, but I'm afraid that if the
attacker can change the kernel command line, he/she has so many ways to
screw up the machine, that removing one won't make a difference.

>> (...)
> > 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);
> 
> I don't know either.  One could argue it *should* be locked down because its
> need appears to reflect a BIOS bug.

Indeed. OTOH if you remove all kernel code that is there solely due to
BIOS bugs, then you can rename Secure Boot to No Boot. Well that's
certainly one way to be secure ;-)
One Thousand Gnomes Dec. 5, 2016, 9:09 p.m.
O> > > Suggested-by: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>  
> > 
> > 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.)"  
> 
> I asked him what he prefers - but no response.


I didn't see that question but "Alan Cox" is probably saner - the
thousand gnomes is an old Linus joke 8)
 
> > i2c-piix4.c:module_param (force, int, 0);
> > i2c-sis630.c:module_param(force, bool, 0);
> > i2c-viapro.c:module_param(force, bool, 0);  
> 
> I don't know either.  One could argue it *should* be locked down because its
> need appears to reflect a BIOS bug.

And none of those should show up in that usage form on a box new enough
to have EFI secure boot. Those that do have i2c busses will report them
via ACPI by that period.

Alan
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Patch hide | download patch | download mbox

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@spacetec.no>");
 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@arcom.com>");
 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)