[PATCH 2/2] mtd: phram,slram: Disable when the kernel is locked down

[PATCH 2/2] mtd: phram,slram: Disable when the kernel is locked down

[Ben Hutchings]

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These drivers allow mapping arbitrary memory ranges as MTD devices.
This should be disabled to preserve the kernel's integrity when it is
locked down.

* Add the HWPARAM flag to the module parameters
* When slram is built-in, it uses __setup() to read kernel parameters,
  so add an explicit check security_locked_down() check

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Matthew Garrett <mjg59@google.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Joern Engel <joern@lazybastard.org>
Cc: linux-mtd@lists.infradead.org
---
 drivers/mtd/devices/phram.c | 6 +++++-
 drivers/mtd/devices/slram.c | 9 ++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/devices/phram.c b/drivers/mtd/devices/phram.c
index c467286ca007..9c18b4bb2ed9 100644
--- a/drivers/mtd/devices/phram.c
+++ b/drivers/mtd/devices/phram.c
@@ -294,7 +294,11 @@ static int phram_param_call(const char *val, const struct kernel_param *kp)
 #endif
 }
 
-module_param_call(phram, phram_param_call, NULL, NULL, 000);
+static const struct kernel_param_ops phram_param_ops = {
+	.set = phram_param_call
+};
+__module_param_call(MODULE_PARAM_PREFIX, phram, &phram_param_ops, NULL,
+		    000, -1, KERNEL_PARAM_FL_HWPARAM | hwparam_iomem);
 MODULE_PARM_DESC(phram, "Memory region to map. \"phram=<name>,<start>,<length>\"");
 
 
diff --git a/drivers/mtd/devices/slram.c b/drivers/mtd/devices/slram.c
index 28131a127d06..d92a2461e2ce 100644
--- a/drivers/mtd/devices/slram.c
+++ b/drivers/mtd/devices/slram.c
@@ -43,6 +43,7 @@
 #include <linux/ioctl.h>
 #include <linux/init.h>
 #include <linux/io.h>
+#include <linux/security.h>
 
 #include <linux/mtd/mtd.h>
 
@@ -65,7 +66,7 @@ typedef struct slram_mtd_list {
 #ifdef MODULE
 static char *map[SLRAM_MAX_DEVICES_PARAMS];
 
-module_param_array(map, charp, NULL, 0);
+module_param_hw_array(map, charp, iomem, NULL, 0);
 MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
 #else
 static char *map;
@@ -281,11 +282,17 @@ static int __init init_slram(void)
 #ifndef MODULE
 	char *devstart;
 	char *devlength;
+	int ret;
 
 	if (!map) {
 		E("slram: not enough parameters.\n");
 		return(-EINVAL);
 	}
+
+	ret = security_locked_down(LOCKDOWN_MODULE_PARAMETERS);
+	if (ret)
+		return ret;
+
 	while (map) {
 		devname = devstart = devlength = NULL;
 

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Re: [PATCH 2/2] mtd: phram, slram: Disable when the kernel is locked down

[Matthew Garrett]

On Fri, Aug 30, 2019 at 11:47 AM Ben Hutchings <ben@decadent.org.uk> wrote:
>
> These drivers allow mapping arbitrary memory ranges as MTD devices.
> This should be disabled to preserve the kernel's integrity when it is
> locked down.
>
> * Add the HWPARAM flag to the module parameters
> * When slram is built-in, it uses __setup() to read kernel parameters,
>   so add an explicit check security_locked_down() check
>
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> Cc: Matthew Garrett <mjg59@google.com>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Joern Engel <joern@lazybastard.org>
> Cc: linux-mtd@lists.infradead.org

Reviewed-by: Matthew Garrett <mjg59@google.com>

James, should I pick patches like this up and send them to you, or
will you queue them directly after they're acked?

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Re: [PATCH 2/2] mtd: phram,slram: Disable when the kernel is locked down

[James Morris]

On Tue, 10 Sep 2019, Matthew Garrett wrote:

> On Fri, Aug 30, 2019 at 11:47 AM Ben Hutchings <ben@decadent.org.uk> wrote:
> >
> > These drivers allow mapping arbitrary memory ranges as MTD devices.
> > This should be disabled to preserve the kernel's integrity when it is
> > locked down.
> >
> > * Add the HWPARAM flag to the module parameters
> > * When slram is built-in, it uses __setup() to read kernel parameters,
> >   so add an explicit check security_locked_down() check
> >
> > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > Cc: Matthew Garrett <mjg59@google.com>
> > Cc: David Howells <dhowells@redhat.com>
> > Cc: Joern Engel <joern@lazybastard.org>
> > Cc: linux-mtd@lists.infradead.org
> 
> Reviewed-by: Matthew Garrett <mjg59@google.com>
> 
> James, should I pick patches like this up and send them to you, or
> will you queue them directly after they're acked?

As long as I'm on the to or cc when they're acked, I can grab them.


-- 
James Morris
<jmorris@namei.org>


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Re: [PATCH 2/2] mtd: phram, slram: Disable when the kernel is locked down

[Richard Weinberger]

On Tue, Sep 10, 2019 at 5:17 PM James Morris <jmorris@namei.org> wrote:
>
> On Tue, 10 Sep 2019, Matthew Garrett wrote:
>
> > On Fri, Aug 30, 2019 at 11:47 AM Ben Hutchings <ben@decadent.org.uk> wrote:
> > >
> > > These drivers allow mapping arbitrary memory ranges as MTD devices.
> > > This should be disabled to preserve the kernel's integrity when it is
> > > locked down.
> > >
> > > * Add the HWPARAM flag to the module parameters
> > > * When slram is built-in, it uses __setup() to read kernel parameters,
> > >   so add an explicit check security_locked_down() check
> > >
> > > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > > Cc: Matthew Garrett <mjg59@google.com>
> > > Cc: David Howells <dhowells@redhat.com>
> > > Cc: Joern Engel <joern@lazybastard.org>
> > > Cc: linux-mtd@lists.infradead.org
> >
> > Reviewed-by: Matthew Garrett <mjg59@google.com>
> >
> > James, should I pick patches like this up and send them to you, or
> > will you queue them directly after they're acked?
>
> As long as I'm on the to or cc when they're acked, I can grab them.

Acked-by: Richard Weinberger <richard@nod.at>

BTW: I don't have 1/2 in my inbox, is it also MTD related?

-- 
Thanks,
//richard

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Re: [PATCH 2/2] mtd: phram,slram: Disable when the kernel is locked down

[Ben Hutchings]

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On Wed, 2019-09-11 at 00:18 +0200, Richard Weinberger wrote:
> On Tue, Sep 10, 2019 at 5:17 PM James Morris <jmorris@namei.org> wrote:
> > On Tue, 10 Sep 2019, Matthew Garrett wrote:
> > 
> > > On Fri, Aug 30, 2019 at 11:47 AM Ben Hutchings <ben@decadent.org.uk> wrote:
> > > > These drivers allow mapping arbitrary memory ranges as MTD devices.
> > > > This should be disabled to preserve the kernel's integrity when it is
> > > > locked down.
> > > > 
> > > > * Add the HWPARAM flag to the module parameters
> > > > * When slram is built-in, it uses __setup() to read kernel parameters,
> > > >   so add an explicit check security_locked_down() check
> > > > 
> > > > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > > > Cc: Matthew Garrett <mjg59@google.com>
> > > > Cc: David Howells <dhowells@redhat.com>
> > > > Cc: Joern Engel <joern@lazybastard.org>
> > > > Cc: linux-mtd@lists.infradead.org
> > > 
> > > Reviewed-by: Matthew Garrett <mjg59@google.com>
> > > 
> > > James, should I pick patches like this up and send them to you, or
> > > will you queue them directly after they're acked?
> > 
> > As long as I'm on the to or cc when they're acked, I can grab them.
> 
> Acked-by: Richard Weinberger <richard@nod.at>
> 
> BTW: I don't have 1/2 in my inbox, is it also MTD related?

No, that was for some other drivers (comedi) that allow setting I/O
addresses from user-space.

Ben.

-- 
Ben Hutchings
The obvious mathematical breakthrough [to break modern encryption]
would be development of an easy way to factor large prime numbers.
                                                           - Bill Gates



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