From ab512805710fa0e4ec6b61fee8a52d044a060009 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Thu, 2 Sep 2021 14:57:32 -0700 Subject: kasan: test: rework kmalloc_oob_right Patch series "kasan: test: avoid crashing the kernel with HW_TAGS", v2. KASAN tests do out-of-bounds and use-after-free accesses. Running the tests works fine for the GENERIC mode, as it uses qurantine and redzones. But the HW_TAGS mode uses neither, and running the tests might crash the kernel. Rework the tests to avoid corrupting kernel memory. This patch (of 8): Rework kmalloc_oob_right() to do these bad access checks: 1. An unaligned access one byte past the requested kmalloc size (can only be detected by KASAN_GENERIC). 2. An aligned access into the first out-of-bounds granule that falls within the aligned kmalloc object. 3. Out-of-bounds access past the aligned kmalloc object. Test #3 deliberately uses a read access to avoid corrupting memory. Otherwise, this test might lead to crashes with the HW_TAGS mode, as it neither uses quarantine nor redzones. Link: https://lkml.kernel.org/r/cover.1628779805.git.andreyknvl@gmail.com Link: https://lkml.kernel.org/r/474aa8b7b538c6737a4c6d0090350af2e1776bef.1628779805.git.andreyknvl@gmail.com Signed-off-by: Andrey Konovalov Reviewed-by: Marco Elver Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Alexander Potapenko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/test_kasan.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) (limited to 'lib/test_kasan.c') diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 8f7b0b2f6e11..1bc3cdd2957f 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -122,12 +122,28 @@ static void kasan_test_exit(struct kunit *test) static void kmalloc_oob_right(struct kunit *test) { char *ptr; - size_t size = 123; + size_t size = 128 - KASAN_GRANULE_SIZE - 5; ptr = kmalloc(size, GFP_KERNEL); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); - KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + OOB_TAG_OFF] = 'x'); + /* + * An unaligned access past the requested kmalloc size. + * Only generic KASAN can precisely detect these. + */ + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) + KUNIT_EXPECT_KASAN_FAIL(test, ptr[size] = 'x'); + + /* + * An aligned access into the first out-of-bounds granule that falls + * within the aligned kmalloc object. + */ + KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + 5] = 'y'); + + /* Out-of-bounds access past the aligned kmalloc object. */ + KUNIT_EXPECT_KASAN_FAIL(test, ptr[0] = + ptr[size + KASAN_GRANULE_SIZE + 5]); + kfree(ptr); } -- cgit