linux-kernel - [PATCH V34 21/29] Lock down /proc/kcore

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Message-Id: <20190622000358.19895-22-matthewgarrett@google.com>
Date:   Fri, 21 Jun 2019 17:03:50 -0700
From:   Matthew Garrett <matthewgarrett@...gle.com>
To:     jmorris@...ei.org
Cc:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>
Subject: [PATCH V34 21/29] Lock down /proc/kcore

From: David Howells <dhowells@...hat.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@...hat.com>
Signed-off-by: Matthew Garrett <mjg59@...gle.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