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Date: Wed, 19 Oct 2022 11:35:40 +0800
From: David Gow <davidgow@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kunit/fortify: Validate __alloc_size attribute results
On Tue, Oct 18, 2022 at 4:27 PM Kees Cook <keescook@...omium.org> wrote:
>
> Validate the effect of the __alloc_size attribute on allocators. If the
> compiler doesn't support __builtin_dynamic_object_size(), skip the test.
>
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> To pass this depends on the following patches:
> https://lore.kernel.org/lkml/20221018073430.never.551-kees@kernel.org/
> https://lore.kernel.org/lkml/20221018082232.never.213-kees@kernel.org/
> To not be skipped, either GCC 12 or Clang is needed.
> ---
While this _looks_ good, I can't actually get the tests to pass on my
machine, with the following all having a
__builtin_dynamic_object_size() of -1:
- kmalloc_node(size++, gfp, NUMA_NO_NODE)
- kzalloc(size++, gfp)
- kzalloc_node(size++, gfp, NUMA_NO_NODE)
- kcalloc(1, size++, gfp)
- kcalloc_node(1, size++, gfp, NUMA_NO_NODE)
- kmalloc_array(1, size++, gfp)
- kmalloc_array_node(1, size++, gfp, NUMA_NO_NODE)
I've been using the following command to run the tests:
./tools/testing/kunit/kunit.py run --kconfig_add CONFIG_FORTIFY_SOURCE=y
And I've also tried it on x86_64 and arm64 under qemu, with both gcc
12.2.0 and clang 14.0.6-2, with the same failures.
Is there a dependency somewhere I've missed? (I've tried it on the
ksefltest/kunit branch, with the mentioned dependencies applied, and
also on your for-next/hardening branch, with the missing patches
applied.)
Cheers,
-- David
> lib/fortify_kunit.c | 92 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 92 insertions(+)
>
> diff --git a/lib/fortify_kunit.c b/lib/fortify_kunit.c
> index 409af07f340a..5076ba11adfd 100644
> --- a/lib/fortify_kunit.c
> +++ b/lib/fortify_kunit.c
> @@ -16,7 +16,10 @@
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> #include <kunit/test.h>
> +#include <linux/device.h>
> #include <linux/string.h>
> +#include <linux/slab.h>
> +#include <linux/vmalloc.h>
>
> static const char array_of_10[] = "this is 10";
> static const char *ptr_of_11 = "this is 11!";
> @@ -60,9 +63,98 @@ static void control_flow_split_test(struct kunit *test)
> KUNIT_EXPECT_EQ(test, want_minus_one(pick), SIZE_MAX);
> }
>
> +#define check_alloc(alloc, free) do { \
> + size_t expected = size; \
> + void *p = alloc; \
> + KUNIT_EXPECT_TRUE_MSG(test, p != NULL, #alloc " failed?!\n"); \
> + KUNIT_EXPECT_EQ_MSG(test, __builtin_dynamic_object_size(p, 1), \
> + expected, \
> + "__alloc_size() not working with " #alloc "\n"); \
> + free; \
> +} while (0)
> +
> +static volatile size_t unknown_size = 50;
> +
> +static void alloc_size_test(struct kunit *test)
> +{
> +#if !__has_builtin(__builtin_dynamic_object_size)
> + kunit_skip(test, "Compiler is missing __builtin_dynamic_object_size() support\n");
> +#else
> + const char device_name[] = "fortify-test";
> + struct device *dev;
> + gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
> + size_t size = unknown_size, prev_size;
> + void *orig;
> +
> + /* kmalloc()-family */
> + check_alloc(kmalloc(size++, gfp), kfree(p));
> + check_alloc(kmalloc_node(size++, gfp, NUMA_NO_NODE), kfree(p));
> + check_alloc(kzalloc(size++, gfp), kfree(p));
> + check_alloc(kzalloc_node(size++, gfp, NUMA_NO_NODE), kfree(p));
> + check_alloc(kcalloc(1, size++, gfp), kfree(p));
> + check_alloc(kcalloc_node(1, size++, gfp, NUMA_NO_NODE), kfree(p));
> + check_alloc(kmalloc_array(1, size++, gfp), kfree(p));
> + check_alloc(kmalloc_array_node(1, size++, gfp, NUMA_NO_NODE), kfree(p));
> + check_alloc(__kmalloc(size++, gfp), kfree(p));
> + check_alloc(__kmalloc_node(size++, gfp, NUMA_NO_NODE), kfree(p));
> +
> + /* kmemdup() */
> + prev_size = size;
> + size = 11;
> + check_alloc(kmemdup("hello there", size, gfp), kfree(p));
> + size = prev_size + 1;
> +
> + /* krealloc()-family */
> + orig = kmalloc(size++, gfp);
> + check_alloc(krealloc(orig, size++, gfp), kfree(p));
> + orig = kmalloc(size++, gfp);
> + check_alloc(krealloc_array(orig, 1, size++, gfp), kfree(p));
> +
> + /* vmalloc()-family */
> + check_alloc(vmalloc(size++), vfree(p));
> + check_alloc(vzalloc(size++), vfree(p));
> + check_alloc(__vmalloc(size++, gfp), vfree(p));
> +
> + /* kvalloc()-family */
> + check_alloc(kvmalloc(size++, gfp), kvfree(p));
> + check_alloc(kvmalloc_node(size++, gfp, NUMA_NO_NODE), kvfree(p));
> + check_alloc(kvzalloc(size++, gfp), kvfree(p));
> + check_alloc(kvzalloc_node(size++, gfp, NUMA_NO_NODE), kvfree(p));
> + check_alloc(kvcalloc(1, size++, gfp), kvfree(p));
> + check_alloc(kvmalloc_array(1, size++, gfp), kvfree(p));
> +
> + /* kvrealloc() */
> + prev_size = size++;
> + orig = kvmalloc(prev_size, gfp);
> + check_alloc(kvrealloc(orig, prev_size, size++, gfp), kfree(p));
> +
> + /* Create dummy device for devm_kmalloc()-family tests. */
> + dev = root_device_register(device_name);
> + KUNIT_ASSERT_FALSE_MSG(test, IS_ERR(dev),
> + "Cannot register test device\n");
> +
> + /* devm_kmalloc()-family */
> + check_alloc(devm_kmalloc(dev, size++, gfp), devm_kfree(dev, p));
> + check_alloc(devm_kzalloc(dev, size++, gfp), devm_kfree(dev, p));
> +
> + /* devm_kmemdup() */
> + prev_size = size;
> + size = 4;
> + check_alloc(devm_kmemdup(dev, "Ohai", size, gfp), devm_kfree(dev, p));
> + size = prev_size + 1;
> +
> + /* devm_kremalloc() */
> + orig = devm_kmalloc(dev, size++, gfp);
> + check_alloc(devm_krealloc(dev, orig, size++, gfp), devm_kfree(dev, p));
> +
> + device_unregister(dev);
> +#endif
> +}
> +
> static struct kunit_case fortify_test_cases[] = {
> KUNIT_CASE(known_sizes_test),
> KUNIT_CASE(control_flow_split_test),
> + KUNIT_CASE(alloc_size_test),
> {}
> };
>
> --
> 2.34.1
>
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