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authorKees Cook <keescook@chromium.org>2014-01-23 15:54:38 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-23 16:36:57 -0800
commit3e2a4c183ace8708c69f589505fb82bb63010ade (patch)
treee201c3d60f39bbe3ba5026417d454553ad2fe073 /lib
parent93e9ef83f40603535ffe6b60498149e75f33aa8f (diff)
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 commit 8404663f81d2 ("ARM: 7527/1: uaccess: explicitly check __user pointer when !CPU_USE_DOMAINS") ever regresses again, for any architecture. Additionally, adds new "user" selftest target, which loads this module. Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug13
-rw-r--r--lib/Makefile1
-rw-r--r--lib/test_user_copy.c110
3 files changed, 124 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 7e37a36b691..e0e2eebf7ab 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1609,6 +1609,19 @@ 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"
diff --git a/lib/Makefile b/lib/Makefile
index b494b9af631..98ec3b86106 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
obj-y += kstrtox.o
obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
obj-$(CONFIG_TEST_MODULE) += test_module.o
+obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
ifeq ($(CONFIG_DEBUG_KOBJECT),y)
CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/test_user_copy.c b/lib/test_user_copy.c
new file mode 100644
index 00000000000..0ecef3e4690
--- /dev/null
+++ b/lib/test_user_copy.c
@@ -0,0 +1,110 @@
+/*
+ * Kernel module for testing copy_to/from_user infrastructure.
+ *
+ * Copyright 2013 Google Inc. All Rights Reserved
+ *
+ * Authors:
+ * Kees Cook <keescook@chromium.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) KBUILD_MODNAME ": " fmt
+
+#include <linux/mman.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+
+#define test(condition, msg) \
+({ \
+ int cond = (condition); \
+ if (cond) \
+ pr_warn("%s\n", msg); \
+ cond; \
+})
+
+static int __init test_user_copy_init(void)
+{
+ int ret = 0;
+ char *kmem;
+ char __user *usermem;
+ char *bad_usermem;
+ unsigned long user_addr;
+ unsigned long value = 0x5A;
+
+ kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
+ if (!kmem)
+ 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 >= (unsigned long)(TASK_SIZE)) {
+ pr_warn("Failed to allocate user memory\n");
+ kfree(kmem);
+ return -ENOMEM;
+ }
+
+ usermem = (char __user *)user_addr;
+ bad_usermem = (char *)user_addr;
+
+ /* Legitimate usage: none of these should fail. */
+ ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
+ "legitimate copy_from_user failed");
+ ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
+ "legitimate copy_to_user failed");
+ ret |= test(get_user(value, (unsigned long __user *)usermem),
+ "legitimate get_user failed");
+ ret |= test(put_user(value, (unsigned long __user *)usermem),
+ "legitimate put_user failed");
+
+ /* Invalid usage: none of these should succeed. */
+ ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
+ PAGE_SIZE),
+ "illegal all-kernel copy_from_user passed");
+ ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
+ PAGE_SIZE),
+ "illegal reversed copy_from_user passed");
+ ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
+ PAGE_SIZE),
+ "illegal all-kernel copy_to_user passed");
+ ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
+ PAGE_SIZE),
+ "illegal reversed copy_to_user passed");
+ ret |= test(!get_user(value, (unsigned long __user *)kmem),
+ "illegal get_user passed");
+ ret |= test(!put_user(value, (unsigned long __user *)kmem),
+ "illegal put_user passed");
+
+ vm_munmap(user_addr, PAGE_SIZE * 2);
+ kfree(kmem);
+
+ if (ret == 0) {
+ pr_info("tests passed.\n");
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+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@chromium.org>");
+MODULE_LICENSE("GPL");