From: David Howells <dhowells@redhat.com>
Date: Wed, 8 Nov 2017 15:11:36 +0000
Subject: [22/29] Lock down module params that specify hardware parameters (eg.
 ioport)
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=d20a28efda02a7ce70b943c15246ea2f07e780f4

Provided an annotation for module parameters that specify hardware
parameters (such as io ports, iomem addresses, irqs, dma channels, fixed
dma buffers and other types).

Suggested-by: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 kernel/params.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

Index: linux/kernel/params.c
===================================================================
--- linux.orig/kernel/params.c
+++ linux/kernel/params.c
@@ -108,13 +108,19 @@ bool parameq(const char *a, const char *
 	return parameqn(a, b, strlen(a)+1);
 }
 
-static void param_check_unsafe(const struct kernel_param *kp)
+static bool param_check_unsafe(const struct kernel_param *kp,
+			       const char *doing)
 {
 	if (kp->flags & KERNEL_PARAM_FL_UNSAFE) {
 		pr_notice("Setting dangerous option %s - tainting kernel\n",
 			  kp->name);
 		add_taint(TAINT_USER, LOCKDEP_STILL_OK);
 	}
+
+	if (kp->flags & KERNEL_PARAM_FL_HWPARAM &&
+	    kernel_is_locked_down("Command line-specified device addresses, irqs and dma channels"))
+		return false;
+	return true;
 }
 
 static int parse_one(char *param,
@@ -144,8 +150,10 @@ static int parse_one(char *param,
 			pr_debug("handling %s with %p\n", param,
 				params[i].ops->set);
 			kernel_param_lock(params[i].mod);
-			param_check_unsafe(&params[i]);
-			err = params[i].ops->set(val, &params[i]);
+			if (param_check_unsafe(&params[i], doing))
+				err = params[i].ops->set(val, &params[i]);
+			else
+				err = -EPERM;
 			kernel_param_unlock(params[i].mod);
 			return err;
 		}
@@ -553,6 +561,12 @@ static ssize_t param_attr_show(struct mo
 	return count;
 }
 
+#ifdef CONFIG_MODULES
+#define mod_name(mod) (mod)->name
+#else
+#define mod_name(mod) "unknown"
+#endif
+
 /* sysfs always hands a nul-terminated string in buf.  We rely on that. */
 static ssize_t param_attr_store(struct module_attribute *mattr,
 				struct module_kobject *mk,
@@ -565,8 +579,10 @@ static ssize_t param_attr_store(struct m
 		return -EPERM;
 
 	kernel_param_lock(mk->mod);
-	param_check_unsafe(attribute->param);
-	err = attribute->param->ops->set(buf, attribute->param);
+	if (param_check_unsafe(attribute->param, mod_name(mk->mod)))
+		err = attribute->param->ops->set(buf, attribute->param);
+	else
+		err = -EPERM;
 	kernel_param_unlock(mk->mod);
 	if (!err)
 		return len;