From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Mon, 9 Sep 2013 22:49:39 +0000 (-0700)
Subject: Restrict /dev/mem and /dev/kmem when securelevel is set.
X-Git-Tag: v4.1.12-92~310^2~10
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3fab26a9585e895ae41ce6462bc389327f9a0e63;p=users%2Fjedix%2Flinux-maple.git

Restrict /dev/mem and /dev/kmem when securelevel is set.

Orabug: 21539498

Allowing users to write to address space provides mechanisms that may permit
modification of the kernel at runtime. Prevent this if securelevel has been
set.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
---

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 93c08e3e4e33c..cca3ab8d89b88 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -167,6 +167,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
 	if (p != *ppos)
 		return -EFBIG;
 
+	if (get_securelevel() > 0)
+		return -EPERM;
+
 	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 
@@ -513,6 +516,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
 	char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 	int err = 0;
 
+	if (get_securelevel() > 0)
+		return -EPERM;
+
 	if (p < (unsigned long) high_memory) {
 		unsigned long to_write = min_t(unsigned long, count,
 					       (unsigned long)high_memory - p);