GCC 12 continues to get smarter about array accesses. The KASAN tests
are expecting to explicitly test out-of-bounds conditions at run-time,
so hide the variable from GCC, to avoid warnings like:
../lib/test_kasan.c: In function 'ksize_uaf':
../lib/test_kasan.c:790:61: warning: array subscript 120 is outside array bounds of 'void[120]' [-Warray-bounds]
790 | KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
| ~~~~~~~~~~~~~~~~~~~~~~^~~~~~
../lib/test_kasan.c:97:9: note: in definition of macro 'KUNIT_EXPECT_KASAN_FAIL'
97 | expression; \
| ^~~~~~~~~~
Cc: Andrey Ryabinin <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
lib/test_kasan.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index c233b1a4e984..58c1b01ccfe2 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -131,6 +131,7 @@ static void kmalloc_oob_right(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+ OPTIMIZER_HIDE_VAR(ptr);
/*
* An unaligned access past the requested kmalloc size.
* Only generic KASAN can precisely detect these.
@@ -159,6 +160,7 @@ static void kmalloc_oob_left(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+ OPTIMIZER_HIDE_VAR(ptr);
KUNIT_EXPECT_KASAN_FAIL(test, *ptr = *(ptr - 1));
kfree(ptr);
}
@@ -171,6 +173,7 @@ static void kmalloc_node_oob_right(struct kunit *test)
ptr = kmalloc_node(size, GFP_KERNEL, 0);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+ OPTIMIZER_HIDE_VAR(ptr);
KUNIT_EXPECT_KASAN_FAIL(test, ptr[0] = ptr[size]);
kfree(ptr);
}
@@ -191,6 +194,7 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+ OPTIMIZER_HIDE_VAR(ptr);
KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + OOB_TAG_OFF] = 0);
kfree(ptr);
@@ -271,6 +275,7 @@ static void kmalloc_large_oob_right(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+ OPTIMIZER_HIDE_VAR(ptr);
KUNIT_EXPECT_KASAN_FAIL(test, ptr[size] = 0);
kfree(ptr);
}
@@ -410,6 +415,8 @@ static void kmalloc_oob_16(struct kunit *test)
ptr2 = kmalloc(sizeof(*ptr2), GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
+ OPTIMIZER_HIDE_VAR(ptr1);
+ OPTIMIZER_HIDE_VAR(ptr2);
KUNIT_EXPECT_KASAN_FAIL(test, *ptr1 = *ptr2);
kfree(ptr1);
kfree(ptr2);
@@ -756,6 +763,8 @@ static void ksize_unpoisons_memory(struct kunit *test)
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
real_size = ksize(ptr);
+ OPTIMIZER_HIDE_VAR(ptr);
+
/* This access shouldn't trigger a KASAN report. */
ptr[size] = 'x';
@@ -778,6 +787,7 @@ static void ksize_uaf(struct kunit *test)
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
kfree(ptr);
+ OPTIMIZER_HIDE_VAR(ptr);
KUNIT_EXPECT_KASAN_FAIL(test, ksize(ptr));
KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[0]);
KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
--
2.32.0
On Wed, 8 Jun 2022 at 23:40, Kees Cook <[email protected]> wrote:
>
> GCC 12 continues to get smarter about array accesses. The KASAN tests
> are expecting to explicitly test out-of-bounds conditions at run-time,
> so hide the variable from GCC, to avoid warnings like:
>
> ../lib/test_kasan.c: In function 'ksize_uaf':
> ../lib/test_kasan.c:790:61: warning: array subscript 120 is outside array bounds of 'void[120]' [-Warray-bounds]
Since this keeps happening, I wonder if we could just pass
'-Wno-array-bounds' ? We already have 'CFLAGS_test_kasan.o += $(call
cc-disable-warning, vla)'.
Although eventually I'd assume all the OPTIMIZE_HIDE_VAR() should be
in place, and hopefully it'll have been the last one. I leave it to
you.
> 790 | KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
> | ~~~~~~~~~~~~~~~~~~~~~~^~~~~~
> ../lib/test_kasan.c:97:9: note: in definition of macro 'KUNIT_EXPECT_KASAN_FAIL'
> 97 | expression; \
> | ^~~~~~~~~~
>
> Cc: Andrey Ryabinin <[email protected]>
> Cc: Alexander Potapenko <[email protected]>
> Cc: Andrey Konovalov <[email protected]>
> Cc: Dmitry Vyukov <[email protected]>
> Cc: Vincenzo Frascino <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
> ---
> lib/test_kasan.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index c233b1a4e984..58c1b01ccfe2 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -131,6 +131,7 @@ static void kmalloc_oob_right(struct kunit *test)
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> /*
> * An unaligned access past the requested kmalloc size.
> * Only generic KASAN can precisely detect these.
> @@ -159,6 +160,7 @@ static void kmalloc_oob_left(struct kunit *test)
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> KUNIT_EXPECT_KASAN_FAIL(test, *ptr = *(ptr - 1));
> kfree(ptr);
> }
> @@ -171,6 +173,7 @@ static void kmalloc_node_oob_right(struct kunit *test)
> ptr = kmalloc_node(size, GFP_KERNEL, 0);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> KUNIT_EXPECT_KASAN_FAIL(test, ptr[0] = ptr[size]);
> kfree(ptr);
> }
> @@ -191,6 +194,7 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + OOB_TAG_OFF] = 0);
>
> kfree(ptr);
> @@ -271,6 +275,7 @@ static void kmalloc_large_oob_right(struct kunit *test)
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> KUNIT_EXPECT_KASAN_FAIL(test, ptr[size] = 0);
> kfree(ptr);
> }
> @@ -410,6 +415,8 @@ static void kmalloc_oob_16(struct kunit *test)
> ptr2 = kmalloc(sizeof(*ptr2), GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
>
> + OPTIMIZER_HIDE_VAR(ptr1);
> + OPTIMIZER_HIDE_VAR(ptr2);
> KUNIT_EXPECT_KASAN_FAIL(test, *ptr1 = *ptr2);
> kfree(ptr1);
> kfree(ptr2);
> @@ -756,6 +763,8 @@ static void ksize_unpoisons_memory(struct kunit *test)
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> real_size = ksize(ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> +
> /* This access shouldn't trigger a KASAN report. */
> ptr[size] = 'x';
>
> @@ -778,6 +787,7 @@ static void ksize_uaf(struct kunit *test)
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> kfree(ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> KUNIT_EXPECT_KASAN_FAIL(test, ksize(ptr));
> KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[0]);
> KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
> --
> 2.32.0
>
> --
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