From 3d7c2262f2dcee5d0b1968e61cd78bc04a4a4cbb Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@srcf.ucam.org>
Date: Fri, 9 Aug 2013 17:58:15 -0400
Subject: [PATCH] Add BSD-style securelevel support
Patch-mainline: Queued in subsystem maintainer repository
Git-repo: https://github.com/mjg59/linux
Git-commit: 3d7c2262f2dcee5d0b1968e61cd78bc04a4a4cbb
References: fate#320387
Provide a coarse-grained runtime configuration option for restricting
userspace's ability to modify the running kernel.
Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
include/linux/security.h | 8 +++
security/Kconfig | 8 +++
security/Makefile | 1
security/securelevel.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 133 insertions(+)
create mode 100644 security/securelevel.c
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1584,6 +1584,14 @@ static inline void security_audit_rule_f
#endif /* CONFIG_SECURITY */
#endif /* CONFIG_AUDIT */
+#ifdef CONFIG_SECURITY_SECURELEVEL
+extern int get_securelevel(void);
+extern int set_securelevel(int new_securelevel);
+#else
+static inline int get_securelevel(void) { return 0; }
+static inline int set_securelevel(int new_securelevel) { return 0; }
+#endif /* CONFIG_SECURELEVEL */
+
#ifdef CONFIG_SECURITYFS
extern struct dentry *securityfs_create_file(const char *name, umode_t mode,
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -71,6 +71,14 @@ config SECURITY_PATH
implement pathname based access controls.
If you are unsure how to answer this question, answer N.
+config SECURITY_SECURELEVEL
+ bool "Securelevel kernel restriction interface"
+ depends on SECURITY
+ help
+ This enables support for adding a set of additional kernel security
+ restrictions at runtime. See Documentation/security/securelevel.txt
+ for further information.
+
config INTEL_TXT
bool "Enable Intel(R) Trusted Execution Technology (Intel(R) TXT)"
depends on HAVE_INTEL_TXT
--- a/security/Makefile
+++ b/security/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_MMU) += min_addr.o
# Object file lists
obj-$(CONFIG_SECURITY) += security.o
obj-$(CONFIG_SECURITYFS) += inode.o
+obj-$(CONFIG_SECURITY_SECURELEVEL) += securelevel.o
obj-$(CONFIG_SECURITY_SELINUX) += selinux/
obj-$(CONFIG_SECURITY_SMACK) += smack/
obj-$(CONFIG_AUDIT) += lsm_audit.o
--- /dev/null
+++ b/security/securelevel.c
@@ -0,0 +1,116 @@
+/*
+ * securelevel.c - support for generic kernel lockdown
+ *
+ * Copyright Nebula, Inc <mjg59@srcf.ucam.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/security.h>
+#include <linux/uaccess.h>
+
+static int securelevel;
+
+static DEFINE_SPINLOCK(securelevel_lock);
+
+#define MAX_SECURELEVEL 1
+
+int get_securelevel(void)
+{
+ return securelevel;
+}
+EXPORT_SYMBOL(get_securelevel);
+
+int set_securelevel(int new_securelevel)
+{
+ int ret = 0;
+
+ spin_lock(&securelevel_lock);
+
+ if ((securelevel == -1) || (new_securelevel < securelevel) ||
+ (new_securelevel > MAX_SECURELEVEL)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ securelevel = new_securelevel;
+out:
+ spin_unlock(&securelevel_lock);
+ return ret;
+}
+EXPORT_SYMBOL(set_securelevel);
+
+static ssize_t securelevel_read(struct file *filp, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ char tmpbuf[12];
+ ssize_t length;
+
+ length = scnprintf(tmpbuf, sizeof(tmpbuf), "%d", securelevel);
+ return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
+}
+
+static ssize_t securelevel_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ char *page = NULL;
+ ssize_t length;
+ int new_securelevel;
+
+ length = -ENOMEM;
+ if (count >= PAGE_SIZE)
+ goto out;
+
+ length = -EINVAL;
+ if (*ppos != 0)
+ goto out;
+
+ length = -ENOMEM;
+ page = (char *)get_zeroed_page(GFP_KERNEL);
+ if (!page)
+ goto out;
+
+ length = -EFAULT;
+ if (copy_from_user(page, buf, count))
+ goto out;
+
+ length = -EINVAL;
+ if (sscanf(page, "%d", &new_securelevel) != 1)
+ goto out;
+
+ length = set_securelevel(new_securelevel);
+ if (length)
+ goto out;
+
+ length = count;
+out:
+ free_page((unsigned long) page);
+ return length;
+}
+
+static const struct file_operations securelevel_fops = {
+ .read = securelevel_read,
+ .write = securelevel_write,
+ .llseek = generic_file_llseek,
+};
+
+static __init int setup_securelevel(void)
+{
+ struct dentry *securelevel_file;
+
+ securelevel_file = securityfs_create_file("securelevel",
+ S_IWUSR | S_IRUGO,
+ NULL, NULL,
+ &securelevel_fops);
+
+ if (IS_ERR(securelevel_file))
+ return PTR_ERR(securelevel_file);
+
+ return 0;
+}
+late_initcall(setup_securelevel);