[PATCH AUTOSEL 5.14 98/99] kasan: test: avoid corrupting memory in copy_user_test

Sasha Levin
2021-09-10T00:47:14Z

From: Andrey Konovalov <andreyknvl@gmail.com>

[ Upstream commit 756e5a47a5ddf0caa3708f922385a92af9d330b5 ]

copy_user_test() does writes past the allocated object. As the result, it
corrupts kernel memory, which might lead to crashes with the HW_TAGS mode,
as it neither uses quarantine nor redzones.

(Technically, this test can't yet be enabled with the HW_TAGS mode, but
this will be implemented in the future.)

Adjust the test to only write memory within the aligned kmalloc object.

Link: https://lkml.kernel.org/r/19bf3a5112ee65b7db88dc731643b657b816c5e8.1628779805.git.andreyknvl@gmail.com
Signed-off-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/test_kasan_module.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c
index f1017f345d6c..fa73b9df0be4 100644
--- a/lib/test_kasan_module.c
+++ b/lib/test_kasan_module.c
@@ -15,13 +15,11 @@

#include "../mm/kasan/kasan.h"

-#define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : KASAN_GRANULE_SIZE)
-
static noinline void __init copy_user_test(void)
{
char *kmem;
char __user *usermem;
- size_t size = 10;
+ size_t size = 128 - KASAN_GRANULE_SIZE;
int __maybe_unused unused;

kmem = kmalloc(size, GFP_KERNEL);
@@ -38,25 +36,25 @@ static noinline void __init copy_user_test(void)
}

pr_info("out-of-bounds in copy_from_user()\n");
- unused = copy_from_user(kmem, usermem, size + 1 + OOB_TAG_OFF);
+ 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 + OOB_TAG_OFF);
+ 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 + OOB_TAG_OFF);
+ 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 + OOB_TAG_OFF);
+ 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 + OOB_TAG_OFF);
+ 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 + OOB_TAG_OFF);
+ 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 + OOB_TAG_OFF);
+ unused = strncpy_from_user(kmem, usermem, size + 1);

vm_munmap((unsigned long)usermem, PAGE_SIZE);
kfree(kmem);
--
2.30.2