Commit 1b1df4c4 authored Feb 24, 2021 by Andrey Konovalov Committed by Linus Torvalds Feb 24, 2021

kasan: adapt kmalloc_uaf2 test to HW_TAGS mode

In the kmalloc_uaf2() test, the pointers to the two allocated memory
blocks might happen to be the same, and the test will fail. With the
software tag-based mode, the probability of the that is 1/254, so it's
hard to observe the failure. For the hardware tag-based mode though,
the probablity is 1/14, which is quite noticable.

Allow up to 16 attempts at generating different tags for the tag-based
modes.

Link: https://linux-review.googlesource.com/id/Ibfa458ef2804ff465d8eb07434a300bf36388d55
Link: https://lkml.kernel.org/r/9cd5cf2f633dcbf55cab801cd26845d2b075cec7.1610733117.git.andreyknvl@google.com


Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 2e4bde6a

lib/test_kasan.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -382,7 +382,9 @@ static void kmalloc_uaf2(struct kunit *test)
		{
		char ptr1, ptr2;
		size_t size = 43;
		int counter = 0;

		again:
		ptr1 = kmalloc(size, GFP_KERNEL);
		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);

		@@ -391,6 +393,15 @@ static void kmalloc_uaf2(struct kunit *test)
		ptr2 = kmalloc(size, GFP_KERNEL);
		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

		/*
		* For tag-based KASAN ptr1 and ptr2 tags might happen to be the same.
		* Allow up to 16 attempts at generating different tags.
		*/
		if (!IS_ENABLED(CONFIG_KASAN_GENERIC) && ptr1 == ptr2 && counter++ < 16) {
		kfree(ptr2);
		goto again;
		}

		KUNIT_EXPECT_KASAN_FAIL(test, ptr1[40] = 'x');
		KUNIT_EXPECT_PTR_NE(test, ptr1, ptr2);