[PATCH] kasan: migrate copy_user_test to kunit

[Sabyrzhan Tasbolatov <snovitoll@gmail.com>]

Migrate the copy_user_test to the KUnit framework to verify out-of-bound
detection via KASAN reports in copy_from_user(), copy_to_user() and
their static functions.

This is the last migrated test in kasan_test_module.c, therefore delete
the file.

In order to detect OOB access in strncpy_from_user(), we need to move
kasan_check_write() to the function beginning to cover
if (can_do_masked_user_access()) {...} branch as well.

Reported-by: Andrey Konovalov <andreyknvl@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=212205
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
---
 lib/strncpy_from_user.c      |  3 +-
 mm/kasan/kasan_test_c.c      | 39 +++++++++++++++++
 mm/kasan/kasan_test_module.c | 81 ------------------------------------
 3 files changed, 41 insertions(+), 82 deletions(-)
 delete mode 100644 mm/kasan/kasan_test_module.c

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 989a12a67872..55c33e4f3c70 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -120,6 +120,8 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
 	if (unlikely(count <= 0))
 		return 0;
 
+	kasan_check_write(dst, count);
+
 	if (can_do_masked_user_access()) {
 		long retval;
 
@@ -142,7 +144,6 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
 		if (max > count)
 			max = count;
 
-		kasan_check_write(dst, count);
 		check_object_size(dst, count, false);
 		if (user_read_access_begin(src, max)) {
 			retval = do_strncpy_from_user(dst, src, count, max);
diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c
index a181e4780d9d..e71a16d0dfb9 100644
--- a/mm/kasan/kasan_test_c.c
+++ b/mm/kasan/kasan_test_c.c
@@ -1954,6 +1954,44 @@ static void rust_uaf(struct kunit *test)
 	KUNIT_EXPECT_KASAN_FAIL(test, kasan_test_rust_uaf());
 }
 
+static void copy_user_test_oob(struct kunit *test)
+{
+	char *kmem;
+	char __user *usermem;
+	unsigned long useraddr;
+	size_t size = 128 - KASAN_GRANULE_SIZE;
+	int __maybe_unused unused;
+
+	kmem = kunit_kmalloc(test, size, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, kmem);
+
+	useraddr = kunit_vm_mmap(test, NULL, 0, PAGE_SIZE,
+					PROT_READ | PROT_WRITE | PROT_EXEC,
+					MAP_ANONYMOUS | MAP_PRIVATE, 0);
+	KUNIT_ASSERT_NE_MSG(test, useraddr, 0,
+		"Could not create userspace mm");
+	KUNIT_ASSERT_LT_MSG(test, useraddr, (unsigned long)TASK_SIZE,
+		"Failed to allocate user memory");
+
+	OPTIMIZER_HIDE_VAR(size);
+	usermem = (char __user *)useraddr;
+
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		unused = copy_from_user(kmem, usermem, size + 1));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		unused = copy_to_user(usermem, kmem, size + 1));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		unused = __copy_from_user(kmem, usermem, size + 1));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		unused = __copy_to_user(usermem, kmem, size + 1));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		unused = __copy_from_user_inatomic(kmem, usermem, size + 1));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		unused = __copy_to_user_inatomic(usermem, kmem, size + 1));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		unused = strncpy_from_user(kmem, usermem, size + 1));
+}
+
 static struct kunit_case kasan_kunit_test_cases[] = {
 	KUNIT_CASE(kmalloc_oob_right),
 	KUNIT_CASE(kmalloc_oob_left),
@@ -2028,6 +2066,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
 	KUNIT_CASE(match_all_ptr_tag),
 	KUNIT_CASE(match_all_mem_tag),
 	KUNIT_CASE(rust_uaf),
+	KUNIT_CASE(copy_user_test_oob),
 	{}
 };
 
diff --git a/mm/kasan/kasan_test_module.c b/mm/kasan/kasan_test_module.c
deleted file mode 100644
index 27ec22767e42..000000000000
--- a/mm/kasan/kasan_test_module.c
+++ /dev/null
@@ -1,81 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- *
- * Copyright (c) 2014 Samsung Electronics Co., Ltd.
- * Author: Andrey Ryabinin <a.ryabinin@samsung.com>
- */
-
-#define pr_fmt(fmt) "kasan: test: " fmt
-
-#include <linux/mman.h>
-#include <linux/module.h>
-#include <linux/printk.h>
-#include <linux/slab.h>
-#include <linux/uaccess.h>
-
-#include "kasan.h"
-
-static noinline void __init copy_user_test(void)
-{
-	char *kmem;
-	char __user *usermem;
-	size_t size = 128 - KASAN_GRANULE_SIZE;
-	int __maybe_unused unused;
-
-	kmem = kmalloc(size, GFP_KERNEL);
-	if (!kmem)
-		return;
-
-	usermem = (char __user *)vm_mmap(NULL, 0, PAGE_SIZE,
-			    PROT_READ | PROT_WRITE | PROT_EXEC,
-			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
-	if (IS_ERR(usermem)) {
-		pr_err("Failed to allocate user memory\n");
-		kfree(kmem);
-		return;
-	}
-
-	OPTIMIZER_HIDE_VAR(size);
-
-	pr_info("out-of-bounds in copy_from_user()\n");
-	unused = copy_from_user(kmem, usermem, size + 1);
-
-	pr_info("out-of-bounds in copy_to_user()\n");
-	unused = copy_to_user(usermem, kmem, size + 1);
-
-	pr_info("out-of-bounds in __copy_from_user()\n");
-	unused = __copy_from_user(kmem, usermem, size + 1);
-
-	pr_info("out-of-bounds in __copy_to_user()\n");
-	unused = __copy_to_user(usermem, kmem, size + 1);
-
-	pr_info("out-of-bounds in __copy_from_user_inatomic()\n");
-	unused = __copy_from_user_inatomic(kmem, usermem, size + 1);
-
-	pr_info("out-of-bounds in __copy_to_user_inatomic()\n");
-	unused = __copy_to_user_inatomic(usermem, kmem, size + 1);
-
-	pr_info("out-of-bounds in strncpy_from_user()\n");
-	unused = strncpy_from_user(kmem, usermem, size + 1);
-
-	vm_munmap((unsigned long)usermem, PAGE_SIZE);
-	kfree(kmem);
-}
-
-static int __init kasan_test_module_init(void)
-{
-	/*
-	 * Temporarily enable multi-shot mode. Otherwise, KASAN would only
-	 * report the first detected bug and panic the kernel if panic_on_warn
-	 * is enabled.
-	 */
-	bool multishot = kasan_save_enable_multi_shot();
-
-	copy_user_test();
-
-	kasan_restore_multi_shot(multishot);
-	return -EAGAIN;
-}
-
-module_init(kasan_test_module_init);
-MODULE_LICENSE("GPL");
-- 
2.34.1