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Message-ID: <CANpmjNP-r3CcgCnenJEbHB5_RNfnFDF7x=4uufLVbqRZtqGd7g@mail.gmail.com>
Date: Wed, 13 Jan 2021 17:26:58 +0100
From: Marco Elver <elver@...gle.com>
To: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Will Deacon <will.deacon@....com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Peter Collingbourne <pcc@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Branislav Rankov <Branislav.Rankov@....com>,
Kevin Brodsky <kevin.brodsky@....com>,
kasan-dev <kasan-dev@...glegroups.com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Memory Management List <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 05/14] kasan: add match-all tag tests
On Wed, 13 Jan 2021 at 17:21, Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> Add 3 new tests for tag-based KASAN modes:
>
> 1. Check that match-all pointer tag is not assigned randomly.
> 2. Check that 0xff works as a match-all pointer tag.
> 3. Check that there are no match-all memory tags.
>
> Note, that test #3 causes a significant number (255) of KASAN reports
> to be printed during execution for the SW_TAGS mode.
>
> Link: https://linux-review.googlesource.com/id/I78f1375efafa162b37f3abcb2c5bc2f3955dfd8e
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
Reviewed-by: Marco Elver <elver@...gle.com>
> ---
> lib/test_kasan.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++
> mm/kasan/kasan.h | 6 ++++
> 2 files changed, 98 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 714ea27fcc3e..f5470bed50b6 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -13,6 +13,7 @@
> #include <linux/mman.h>
> #include <linux/module.h>
> #include <linux/printk.h>
> +#include <linux/random.h>
> #include <linux/slab.h>
> #include <linux/string.h>
> #include <linux/uaccess.h>
> @@ -754,6 +755,94 @@ static void vmalloc_oob(struct kunit *test)
> vfree(area);
> }
>
> +/*
> + * Check that the assigned pointer tag falls within the [KASAN_TAG_MIN,
> + * KASAN_TAG_KERNEL) range (note: excluding the match-all tag) for tag-based
> + * modes.
> + */
> +static void match_all_not_assigned(struct kunit *test)
> +{
> + char *ptr;
> + struct page *pages;
> + int i, size, order;
> +
> + KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);
> +
> + for (i = 0; i < 256; i++) {
> + size = get_random_int() % 1024;
> + ptr = kmalloc(size, GFP_KERNEL);
> + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> + KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);
> + KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);
> + kfree(ptr);
> + }
> +
> + for (i = 0; i < 256; i++) {
> + order = get_random_int() % 4;
> + pages = alloc_pages(GFP_KERNEL, order);
> + ptr = page_address(pages);
> + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> + KUNIT_EXPECT_GE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_MIN);
> + KUNIT_EXPECT_LT(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);
> + free_pages((unsigned long)ptr, order);
> + }
> +}
> +
> +/* Check that 0xff works as a match-all pointer tag for tag-based modes. */
> +static void match_all_ptr_tag(struct kunit *test)
> +{
> + char *ptr;
> + u8 tag;
> +
> + KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);
> +
> + ptr = kmalloc(128, GFP_KERNEL);
> + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> +
> + /* Backup the assigned tag. */
> + tag = get_tag(ptr);
> + KUNIT_EXPECT_NE(test, tag, (u8)KASAN_TAG_KERNEL);
> +
> + /* Reset the tag to 0xff.*/
> + ptr = set_tag(ptr, KASAN_TAG_KERNEL);
> +
> + /* This access shouldn't trigger a KASAN report. */
> + *ptr = 0;
> +
> + /* Recover the pointer tag and free. */
> + ptr = set_tag(ptr, tag);
> + kfree(ptr);
> +}
> +
> +/* Check that there are no match-all memory tags for tag-based modes. */
> +static void match_all_mem_tag(struct kunit *test)
> +{
> + char *ptr;
> + int tag;
> +
> + KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);
> +
> + ptr = kmalloc(128, GFP_KERNEL);
> + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> + KUNIT_EXPECT_NE(test, (u8)get_tag(ptr), (u8)KASAN_TAG_KERNEL);
> +
> + /* For each possible tag value not matching the pointer tag. */
> + for (tag = KASAN_TAG_MIN; tag <= KASAN_TAG_KERNEL; tag++) {
> + if (tag == get_tag(ptr))
> + continue;
> +
> + /* Mark the first memory granule with the chosen memory tag. */
> + kasan_poison(ptr, KASAN_GRANULE_SIZE, (u8)tag);
> +
> + /* This access must cause a KASAN report. */
> + KUNIT_EXPECT_KASAN_FAIL(test, *ptr = 0);
> + }
> +
> + /* Recover the memory tag and free. */
> + kasan_poison(ptr, KASAN_GRANULE_SIZE, get_tag(ptr));
> + kfree(ptr);
> +}
> +
> static struct kunit_case kasan_kunit_test_cases[] = {
> KUNIT_CASE(kmalloc_oob_right),
> KUNIT_CASE(kmalloc_oob_left),
> @@ -793,6 +882,9 @@ static struct kunit_case kasan_kunit_test_cases[] = {
> KUNIT_CASE(kasan_bitops_tags),
> KUNIT_CASE(kmalloc_double_kzfree),
> KUNIT_CASE(vmalloc_oob),
> + KUNIT_CASE(match_all_not_assigned),
> + KUNIT_CASE(match_all_ptr_tag),
> + KUNIT_CASE(match_all_mem_tag),
> {}
> };
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 3b38baddec47..c3fb9bf241d3 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -36,6 +36,12 @@ extern bool kasan_flag_panic __ro_after_init;
> #define KASAN_TAG_INVALID 0xFE /* inaccessible memory tag */
> #define KASAN_TAG_MAX 0xFD /* maximum value for random tags */
>
> +#ifdef CONFIG_KASAN_HW_TAGS
> +#define KASAN_TAG_MIN 0xF0 /* mimimum value for random tags */
> +#else
> +#define KASAN_TAG_MIN 0x00 /* mimimum value for random tags */
> +#endif
> +
> #ifdef CONFIG_KASAN_GENERIC
> #define KASAN_FREE_PAGE 0xFF /* page was freed */
> #define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocations */
> --
> 2.30.0.284.gd98b1dd5eaa7-goog
>
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