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Date: Tue, 3 Dec 2013 13:27:34 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
David Howells <dhowells@...hat.com>,
Rusty Russell <rusty@...tcorp.com.au>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
keescook@...omium.org
Subject: [PATCH 2/2] test: check copy_to/from_user boundary validation
To help avoid an architecture failing to correctly check kernel/user
boundaries when handling copy_to_user, copy_from_user, put_user, or
get_user, perform some simple tests and fail to load if any of them
behave unexpectedly.
Specifically, this is to make sure there is a way to notice if things
like what was fixed in 8404663f81d212918ff85f493649a7991209fa04 ("ARM:
7527/1: uaccess: explicitly check __user pointer when !CPU_USE_DOMAINS")
ever regresses again, for any architecture.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
kernel/Makefile | 1 +
kernel/test_user_copy.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 13 ++++++
3 files changed, 117 insertions(+)
create mode 100644 kernel/test_user_copy.c
diff --git a/kernel/Makefile b/kernel/Makefile
index 9de0f0e89937..f8185152cbb8 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -60,6 +60,7 @@ obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o
obj-$(CONFIG_SMP) += stop_machine.o
obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
obj-$(CONFIG_TEST_MODULE) += test_module.o
+obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
obj-$(CONFIG_AUDIT_WATCH) += audit_watch.o
diff --git a/kernel/test_user_copy.c b/kernel/test_user_copy.c
new file mode 100644
index 000000000000..dbf62ec80e48
--- /dev/null
+++ b/kernel/test_user_copy.c
@@ -0,0 +1,103 @@
+/*
+ * Kernel module for testing copy_to/from_user infrastructure.
+ *
+ * Copyright 2013 Google Inc. All Rights Reserved
+ *
+ * Authors:
+ * Kees Cook <keescook@...omium.org>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) "test_user_copy: " fmt
+
+#include <linux/mman.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+
+#define failed(msg) { \
+ pr_warn(msg); \
+ ret = -EINVAL; \
+}
+
+static int __init test_user_copy_init(void)
+{
+ int ret = 0;
+ char *kmem;
+ char __user *usermem;
+ unsigned long user_addr;
+ unsigned long value = 0x5A;
+
+ kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
+ if (!kmem) {
+ pr_warn("Failed to allocate kernel memory\n");
+ return -ENOMEM;
+ }
+
+ user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
+ PROT_READ | PROT_WRITE | PROT_EXEC,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0);
+ if (user_addr >= TASK_SIZE) {
+ pr_warn("Failed to allocate user memory\n");
+ kfree(kmem);
+ return -ENOMEM;
+ }
+
+ usermem = (char __user *)user_addr;
+
+ /* Legitimate usage: none of these should fail. */
+ if (copy_from_user(kmem, usermem, PAGE_SIZE))
+ failed("legitimate copy_from_user failed");
+ if (copy_to_user(usermem, kmem, PAGE_SIZE))
+ failed("legitimate copy_to_user failed");
+ if (get_user(value, (unsigned long __user *)usermem))
+ failed("legitimate get_user failed");
+ if (put_user(value, (unsigned long __user *)usermem))
+ failed("legitimate put_user failed");
+
+ /* Invalid usage: none of these should succeed. */
+ if (!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
+ PAGE_SIZE))
+ failed("illegal all-kernel copy_from_user passed");
+ if (!copy_from_user((char *)usermem, (char __user *)kmem, PAGE_SIZE))
+ failed("illegal reversed copy_from_user passed");
+
+ if (!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE, PAGE_SIZE))
+ failed("illegal all-kernel copy_to_user passed");
+ if (!copy_to_user((char __user *)kmem, (char *)usermem, PAGE_SIZE))
+ failed("illegal reversed copy_to_user passed");
+
+ if (!get_user(value, (unsigned long __user *)kmem))
+ failed("illegal get_user passed");
+ if (!put_user(value, (unsigned long __user *)kmem))
+ failed("illegal put_user passed");
+
+ vm_munmap(user_addr, PAGE_SIZE * 2);
+ kfree(kmem);
+
+ if (ret == 0)
+ pr_info("tests passed.\n");
+
+ return ret;
+}
+
+module_init(test_user_copy_init);
+
+static void __exit test_user_copy_exit(void)
+{
+ pr_info("unloaded.\n");
+}
+
+module_exit(test_user_copy_exit);
+
+MODULE_AUTHOR("Kees Cook <keescook@...omium.org>");
+MODULE_LICENSE("GPL");
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 20abc92032e0..92d1a39f885e 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1592,6 +1592,19 @@ config TEST_MODULE
If unsure, say N.
+config TEST_USER_COPY
+ tristate "Test user/kernel boundary protections"
+ default n
+ depends on m
+ help
+ This builds the "test_user_copy" module that runs sanity checks
+ on the copy_to/from_user infrastructure, making sure basic
+ user/kernel boundary testing is working. If it fails to load,
+ a regression has been detected in the user/kernel memory boundary
+ protections.
+
+ If unsure, say N.
+
source "samples/Kconfig"
source "lib/Kconfig.kgdb"
--
1.7.9.5
--
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