kernel/Restrict-dev-mem-and-dev-kmem-when-module-loading-is.patch

From 9f31204f829da97f99f7aacf30f0ddc26e456df7 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Fri, 9 Mar 2012 09:28:15 -0500
Subject: [PATCH 06/20] Restrict /dev/mem and /dev/kmem when module loading is
 restricted

Allowing users to write to address space makes it possible for the kernel
to be subverted, avoiding module loading restrictions. Prevent this when
any restrictions have been imposed on loading modules.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 drivers/char/mem.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 7f1a7ab5850d..d6a6f05fbc1c 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -164,6 +164,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
 	if (p != *ppos)
 		return -EFBIG;
 
+	if (secure_modules())
+		return -EPERM;
+
 	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 
@@ -516,6 +519,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
 	if (!pfn_valid(PFN_DOWN(p)))
 		return -EIO;
 
+	if (secure_modules())
+		return -EPERM;
+
 	if (p < (unsigned long) high_memory) {
 		unsigned long to_write = min_t(unsigned long, count,
 					       (unsigned long)high_memory - p);
-- 
2.9.3