path: root/drivers
diff options
authorMatthew Garrett <mjg59@srcf.ucam.org>2019-08-19 17:17:41 -0700
committerJames Morris <jmorris@namei.org>2019-08-19 21:54:15 -0700
commit9b9d8dda1ed72e9bd560ab0ca93d322a9440510e (patch)
treeaa5a6719f76556e20ce1ca6e286d10660f1746f5 /drivers
parentlockdown: Enforce module signatures if the kernel is locked down (diff)
lockdown: Restrict /dev/{mem,kmem,port} when the kernel is locked down
Allowing users to read and write to core kernel memory makes it possible for the kernel to be subverted, avoiding module loading restrictions, and also to steal cryptographic information. Disallow /dev/mem and /dev/kmem from being opened this when the kernel has been locked down to prevent this. Also disallow /dev/port from being opened to prevent raw ioport access and thus DMA from being used to accomplish the same thing. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <mjg59@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: x86@kernel.org Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'drivers')
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index b08dc50f9f26..d0148aee1aab 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -29,8 +29,8 @@
#include <linux/export.h>
#include <linux/io.h>
#include <linux/uio.h>
#include <linux/uaccess.h>
+#include <linux/security.h>
#ifdef CONFIG_IA64
# include <linux/efi.h>
@@ -786,7 +786,10 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
static int open_port(struct inode *inode, struct file *filp)
- return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
+ if (!capable(CAP_SYS_RAWIO))
+ return -EPERM;
+ return security_locked_down(LOCKDOWN_DEV_MEM);
#define zero_lseek null_lseek