39 lines
1.2 KiB
Diff
39 lines
1.2 KiB
Diff
From: Matthew Garrett <matthew.garrett@nebula.com>
|
|
Date: Wed, 5 Apr 2017 17:40:30 +0100
|
|
Subject: [42/61] Restrict /dev/mem and /dev/kmem when the kernel is locked
|
|
down
|
|
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=104cff827b18e35874153bd8df14eba59e5b411a
|
|
|
|
Allowing users to write to address space makes it possible for the kernel to
|
|
be subverted, avoiding module loading restrictions. Prevent this when the
|
|
kernel has been locked down.
|
|
|
|
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
|
|
Signed-off-by: David Howells <dhowells@redhat.com>
|
|
---
|
|
drivers/char/mem.c | 6 ++++++
|
|
1 file changed, 6 insertions(+)
|
|
|
|
--- a/drivers/char/mem.c
|
|
+++ b/drivers/char/mem.c
|
|
@@ -179,6 +179,9 @@ static ssize_t write_mem(struct file *fi
|
|
if (p != *ppos)
|
|
return -EFBIG;
|
|
|
|
+ if (kernel_is_locked_down())
|
|
+ return -EPERM;
|
|
+
|
|
if (!valid_phys_addr_range(p, count))
|
|
return -EFAULT;
|
|
|
|
@@ -540,6 +543,9 @@ static ssize_t write_kmem(struct file *f
|
|
char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
|
|
int err = 0;
|
|
|
|
+ if (kernel_is_locked_down())
|
|
+ return -EPERM;
|
|
+
|
|
if (p < (unsigned long) high_memory) {
|
|
unsigned long to_write = min_t(unsigned long, count,
|
|
(unsigned long)high_memory - p);
|