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    Subject[PATCH v3 05/15] kasan: add match-all tag tests
    From
    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
    Reviewed-by: Marco Elver <elver@google.com>
    Signed-off-by: Andrey Konovalov <andreyknvl@google.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..c344fe506ffc 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) + 1;
    + 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) + 1;
    + 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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