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Date: Wed, 6 Oct 2021 11:15:44 -0700 From: Kees Cook <keescook@...omium.org> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Kees Cook <keescook@...omium.org>, Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com, Jann Horn <jannh@...gle.com>, Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: [PATCH v2] kasan: test: Bypass __alloc_size checks Intentional overflows, as performed by the KASAN tests, are detected at compile time[1] (instead of only at run-time) with the addition of __alloc_size. Fix this by forcing the compiler into not being able to trust the size used following the kmalloc()s. [1] https://lore.kernel.org/lkml/20211005184717.65c6d8eb39350395e387b71f@linux-foundation.org Cc: Andrey Ryabinin <ryabinin.a.a@...il.com> Cc: Alexander Potapenko <glider@...gle.com> Cc: Andrey Konovalov <andreyknvl@...il.com> Cc: Dmitry Vyukov <dvyukov@...gle.com> Cc: kasan-dev@...glegroups.com Signed-off-by: Kees Cook <keescook@...omium.org> --- v2: use OPTIMIZER_HIDE_VAR() (jann, mark) v1: https://lore.kernel.org/lkml/20211006035522.539346-1-keescook@chromium.org/ --- lib/test_kasan.c | 8 +++++++- lib/test_kasan_module.c | 2 ++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 8835e0784578..8a8a8133f4cd 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -440,6 +440,7 @@ static void kmalloc_oob_memset_2(struct kunit *test) ptr = kmalloc(size, GFP_KERNEL); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + OPTIMIZER_HIDE_VAR(size); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2)); kfree(ptr); } @@ -452,6 +453,7 @@ static void kmalloc_oob_memset_4(struct kunit *test) ptr = kmalloc(size, GFP_KERNEL); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + OPTIMIZER_HIDE_VAR(size); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4)); kfree(ptr); } @@ -464,6 +466,7 @@ static void kmalloc_oob_memset_8(struct kunit *test) ptr = kmalloc(size, GFP_KERNEL); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + OPTIMIZER_HIDE_VAR(size); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8)); kfree(ptr); } @@ -476,6 +479,7 @@ static void kmalloc_oob_memset_16(struct kunit *test) ptr = kmalloc(size, GFP_KERNEL); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + OPTIMIZER_HIDE_VAR(size); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16)); kfree(ptr); } @@ -488,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test) ptr = kmalloc(size, GFP_KERNEL); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + OPTIMIZER_HIDE_VAR(size); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr, 0, size + KASAN_GRANULE_SIZE)); kfree(ptr); @@ -497,7 +502,7 @@ static void kmalloc_memmove_invalid_size(struct kunit *test) { char *ptr; size_t size = 64; - volatile size_t invalid_size = -2; + size_t invalid_size = -2; /* * Hardware tag-based mode doesn't check memmove for negative size. @@ -510,6 +515,7 @@ static void kmalloc_memmove_invalid_size(struct kunit *test) KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); memset((char *)ptr, 0, 64); + OPTIMIZER_HIDE_VAR(invalid_size); KUNIT_EXPECT_KASAN_FAIL(test, memmove((char *)ptr, (char *)ptr + 4, invalid_size)); kfree(ptr); diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c index 7ebf433edef3..b112cbc835e9 100644 --- a/lib/test_kasan_module.c +++ b/lib/test_kasan_module.c @@ -35,6 +35,8 @@ static noinline void __init copy_user_test(void) return; } + OPTIMIZER_HIDE_VAR(size); + pr_info("out-of-bounds in copy_from_user()\n"); unused = copy_from_user(kmem, usermem, size + 1); -- 2.30.2
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