linux-kernel - [PATCH 34/38] Annotate hardware config module parameters in fs/pstore/

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Date:   Wed, 05 Apr 2017 18:01:51 +0100
From:   David Howells <dhowells@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     gnomes@...rguk.ukuu.org.uk, Tony Luck <tony.luck@...el.com>,
        Kees Cook <keescook@...omium.org>, gregkh@...uxfoundation.org,
        Anton Vorontsov <anton@...msg.org>, dhowells@...hat.com,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        Colin Cross <ccross@...roid.com>
Subject: [PATCH 34/38] Annotate hardware config module parameters in
 fs/pstore/

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 fs/pstore/.

Suggested-by: Alan Cox <gnomes@...rguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Anton Vorontsov <anton@...msg.org>
cc: Colin Cross <ccross@...roid.com>
cc: Kees Cook <keescook@...omium.org>
cc: Tony Luck <tony.luck@...el.com>
---

 fs/pstore/ram.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 11f918d34b1e..cce1d38417ca 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -58,7 +58,7 @@ module_param_named(pmsg_size, ramoops_pmsg_size, ulong, 0400);
 MODULE_PARM_DESC(pmsg_size, "size of user space message log");

 static unsigned long long mem_address;
-module_param(mem_address, ullong, 0400);
+module_param_hw(mem_address, ullong, other, 0400);
 MODULE_PARM_DESC(mem_address,
 		"start of reserved RAM used to store oops/panic logs");