[PATCH V34 21/29] Lock down /proc/kcore

Matthew Garrett
2019-06-22T00:05:01Z

From: David Howells <dhowells@redhat.com>

Disallow access to /proc/kcore when the kernel is locked down to prevent
access to cryptographic data. This is limited to lockdown
confidentiality mode and is still permitted in integrity mode.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
---
fs/proc/kcore.c | 5 +++++
include/linux/security.h | 1 +
security/lockdown/lockdown.c | 1 +
3 files changed, 7 insertions(+)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index d29d869abec1..4e95edb1e282 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -31,6 +31,7 @@
#include <linux/ioport.h>
#include <linux/memory.h>
#include <linux/sched/task.h>
+#include <linux/security.h>
#include <asm/sections.h>
#include "internal.h"

@@ -545,6 +546,10 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)

static int open_kcore(struct inode *inode, struct file *filp)
{
+ int ret = security_locked_down(LOCKDOWN_KCORE);
+
+ if (ret)
+ return ret;
if (!capable(CAP_SYS_RAWIO))
return -EPERM;

diff --git a/include/linux/security.h b/include/linux/security.h
index c649cb91e762..3875f6df2ecc 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -95,6 +95,7 @@ enum lockdown_reason {
LOCKDOWN_MODULE_PARAMETERS,
LOCKDOWN_MMIOTRACE,
LOCKDOWN_INTEGRITY_MAX,
+ LOCKDOWN_KCORE,
LOCKDOWN_CONFIDENTIALITY_MAX,
};

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index cd86ed9f4d4b..4c9b324dfc55 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -31,6 +31,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
[LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters",
[LOCKDOWN_MMIOTRACE] = "unsafe mmio",
[LOCKDOWN_INTEGRITY_MAX] = "integrity",
+ [LOCKDOWN_KCORE] = "/proc/kcore access",
[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
};

--
2.22.0.410.gd8fdbe21b5-goog