Instrument copy_from_kernel_nofault(), copy_to_kernel_nofault(),
strncpy_from_kernel_nofault() where __put_kernel_nofault, __get_kernel_nofault
macros are used.
__get_kernel_nofault needs instrument_memcpy_before() which handles
KASAN, KCSAN checks for src, dst address, whereas for __put_kernel_nofault
macro, instrument_write() check should be enough as it's validated via
kmsan_copy_to_user() in instrument_put_user().
__get_user_size was appended with instrument_get_user() for KMSAN check in
commit 888f84a6da4d("x86: asm: instrument usercopy in get_user() and
put_user()") but only for CONFIG_CC_HAS_ASM_GOTO_OUTPUT.
copy_from_to_kernel_nofault() kunit test triggers 4 KASAN bug reports as
expected per each copy_from/to_kernel_nofault call.
Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=210505
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
---
v2: added 2 tests for src, dst check and enhanced instrument check in macros
On Wed, Sep 18, 2024 at 3:51 AM Andrey Konovalov <andreyknvl@xxxxxxxxx> wrote:
>
> On Tue, Sep 17, 2024 at 10:18 PM Sabyrzhan Tasbolatov
> <snovitoll@xxxxxxxxx> wrote:
> >
> I think the easiest fix would be to allocate e.g. 128 -
> KASAN_GRANULE_SIZE bytes and do an out-of-bounds up to 128 bytes via
> copy_to/from_kernel_nofault. This will only corrupt the in-object
> kmalloc redzone, which is not harmful.
Hi Andrey,
Thanks for the comments. I've changed the target UAF buffer size to
KASAN_GRANULE_SIZE and added other test cases from bugzilla.
---
arch/x86/include/asm/uaccess.h | 4 ++++
mm/kasan/kasan_test.c | 21 +++++++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 3a7755c1a441..bd1ee79238a2 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -353,6 +353,7 @@ do { \
default: \
(x) = __get_user_bad(); \
} \
+ instrument_get_user(x); \
} while (0)
#define __get_user_asm(x, addr, err, itype) \
@@ -620,6 +621,7 @@ do { \
#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
#define __get_kernel_nofault(dst, src, type, err_label) \
+ instrument_memcpy_before(dst, src, sizeof(type)); \
__get_user_size(*((type *)(dst)), (__force type __user *)(src), \
sizeof(type), err_label)
#else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
@@ -627,6 +629,7 @@ do { \
do { \
int __kr_err; \
\
+ instrument_memcpy_before(dst, src, sizeof(type)); \
__get_user_size(*((type *)(dst)), (__force type __user *)(src), \
sizeof(type), __kr_err); \
if (unlikely(__kr_err)) \
@@ -635,6 +638,7 @@ do { \
#endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
#define __put_kernel_nofault(dst, src, type, err_label) \
+ instrument_write(dst, sizeof(type)); \
__put_user_size(*((type *)(src)), (__force type __user *)(dst), \
sizeof(type), err_label)
diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 7b32be2a3cf0..9a3c4ad91d59 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -1899,6 +1899,26 @@ static void match_all_mem_tag(struct kunit *test)
kfree(ptr);
}
+static void copy_from_to_kernel_nofault(struct kunit *test)
+{
+ char *ptr;
+ char buf[KASAN_GRANULE_SIZE];
+ size_t size = sizeof(buf);
+
+ ptr = kmalloc(size, GFP_KERNEL);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+ kfree(ptr);
+
+ KUNIT_EXPECT_KASAN_FAIL(test,
+ copy_from_kernel_nofault(&buf[0], ptr, size));
+ KUNIT_EXPECT_KASAN_FAIL(test,
+ copy_from_kernel_nofault(ptr, &buf[0], size));
+ KUNIT_EXPECT_KASAN_FAIL(test,
+ copy_to_kernel_nofault(&buf[0], ptr, size));
+ KUNIT_EXPECT_KASAN_FAIL(test,
+ copy_to_kernel_nofault(ptr, &buf[0], size));
+}
+
static struct kunit_case kasan_kunit_test_cases[] = {
KUNIT_CASE(kmalloc_oob_right),
KUNIT_CASE(kmalloc_oob_left),
@@ -1971,6 +1991,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
KUNIT_CASE(match_all_not_assigned),
KUNIT_CASE(match_all_ptr_tag),
KUNIT_CASE(match_all_mem_tag),
+ KUNIT_CASE(copy_from_to_kernel_nofault),
{}
};
--
2.34.1
